Update dependencies (#1784)

6 files changed, 1742 insertions, 0 deletions

diff --git a/vendor/github.com/graph-gophers/graphql-go/internal/exec/exec.go b/vendor/github.com/graph-gophers/graphql-go/internal/exec/exec.go
new file mode 100644
index 00000000..6b478487
--- /dev/null
+++ b/vendor/github.com/graph-gophers/graphql-go/internal/exec/exec.go
@@ -0,0 +1,381 @@
+package exec
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"reflect"
+	"sync"
+	"time"
+
+	"github.com/graph-gophers/graphql-go/errors"
+	"github.com/graph-gophers/graphql-go/internal/exec/resolvable"
+	"github.com/graph-gophers/graphql-go/internal/exec/selected"
+	"github.com/graph-gophers/graphql-go/internal/query"
+	"github.com/graph-gophers/graphql-go/log"
+	"github.com/graph-gophers/graphql-go/trace"
+	"github.com/graph-gophers/graphql-go/types"
+)
+
+type Request struct {
+	selected.Request
+	Limiter                  chan struct{}
+	Tracer                   trace.Tracer
+	Logger                   log.Logger
+	PanicHandler             errors.PanicHandler
+	SubscribeResolverTimeout time.Duration
+}
+
+func (r *Request) handlePanic(ctx context.Context) {
+	if value := recover(); value != nil {
+		r.Logger.LogPanic(ctx, value)
+		r.AddError(r.PanicHandler.MakePanicError(ctx, value))
+	}
+}
+
+type extensionser interface {
+	Extensions() map[string]interface{}
+}
+
+func (r *Request) Execute(ctx context.Context, s *resolvable.Schema, op *types.OperationDefinition) ([]byte, []*errors.QueryError) {
+	var out bytes.Buffer
+	func() {
+		defer r.handlePanic(ctx)
+		sels := selected.ApplyOperation(&r.Request, s, op)
+		r.execSelections(ctx, sels, nil, s, s.Resolver, &out, op.Type == query.Mutation)
+	}()
+
+	if err := ctx.Err(); err != nil {
+		return nil, []*errors.QueryError{errors.Errorf("%s", err)}
+	}
+
+	return out.Bytes(), r.Errs
+}
+
+type fieldToExec struct {
+	field    *selected.SchemaField
+	sels     []selected.Selection
+	resolver reflect.Value
+	out      *bytes.Buffer
+}
+
+func resolvedToNull(b *bytes.Buffer) bool {
+	return bytes.Equal(b.Bytes(), []byte("null"))
+}
+
+func (r *Request) execSelections(ctx context.Context, sels []selected.Selection, path *pathSegment, s *resolvable.Schema, resolver reflect.Value, out *bytes.Buffer, serially bool) {
+	async := !serially && selected.HasAsyncSel(sels)
+
+	var fields []*fieldToExec
+	collectFieldsToResolve(sels, s, resolver, &fields, make(map[string]*fieldToExec))
+
+	if async {
+		var wg sync.WaitGroup
+		wg.Add(len(fields))
+		for _, f := range fields {
+			go func(f *fieldToExec) {
+				defer wg.Done()
+				defer r.handlePanic(ctx)
+				f.out = new(bytes.Buffer)
+				execFieldSelection(ctx, r, s, f, &pathSegment{path, f.field.Alias}, true)
+			}(f)
+		}
+		wg.Wait()
+	} else {
+		for _, f := range fields {
+			f.out = new(bytes.Buffer)
+			execFieldSelection(ctx, r, s, f, &pathSegment{path, f.field.Alias}, true)
+		}
+	}
+
+	out.WriteByte('{')
+	for i, f := range fields {
+		// If a non-nullable child resolved to null, an error was added to the
+		// "errors" list in the response, so this field resolves to null.
+		// If this field is non-nullable, the error is propagated to its parent.
+		if _, ok := f.field.Type.(*types.NonNull); ok && resolvedToNull(f.out) {
+			out.Reset()
+			out.Write([]byte("null"))
+			return
+		}
+
+		if i > 0 {
+			out.WriteByte(',')
+		}
+		out.WriteByte('"')
+		out.WriteString(f.field.Alias)
+		out.WriteByte('"')
+		out.WriteByte(':')
+		out.Write(f.out.Bytes())
+	}
+	out.WriteByte('}')
+}
+
+func collectFieldsToResolve(sels []selected.Selection, s *resolvable.Schema, resolver reflect.Value, fields *[]*fieldToExec, fieldByAlias map[string]*fieldToExec) {
+	for _, sel := range sels {
+		switch sel := sel.(type) {
+		case *selected.SchemaField:
+			field, ok := fieldByAlias[sel.Alias]
+			if !ok { // validation already checked for conflict (TODO)
+				field = &fieldToExec{field: sel, resolver: resolver}
+				fieldByAlias[sel.Alias] = field
+				*fields = append(*fields, field)
+			}
+			field.sels = append(field.sels, sel.Sels...)
+
+		case *selected.TypenameField:
+			_, ok := fieldByAlias[sel.Alias]
+			if !ok {
+				res := reflect.ValueOf(typeOf(sel, resolver))
+				f := s.FieldTypename
+				f.TypeName = res.String()
+
+				sf := &selected.SchemaField{
+					Field:       f,
+					Alias:       sel.Alias,
+					FixedResult: res,
+				}
+
+				field := &fieldToExec{field: sf, resolver: resolver}
+				*fields = append(*fields, field)
+				fieldByAlias[sel.Alias] = field
+			}
+
+		case *selected.TypeAssertion:
+			out := resolver.Method(sel.MethodIndex).Call(nil)
+			if !out[1].Bool() {
+				continue
+			}
+			collectFieldsToResolve(sel.Sels, s, out[0], fields, fieldByAlias)
+
+		default:
+			panic("unreachable")
+		}
+	}
+}
+
+func typeOf(tf *selected.TypenameField, resolver reflect.Value) string {
+	if len(tf.TypeAssertions) == 0 {
+		return tf.Name
+	}
+	for name, a := range tf.TypeAssertions {
+		out := resolver.Method(a.MethodIndex).Call(nil)
+		if out[1].Bool() {
+			return name
+		}
+	}
+	return ""
+}
+
+func execFieldSelection(ctx context.Context, r *Request, s *resolvable.Schema, f *fieldToExec, path *pathSegment, applyLimiter bool) {
+	if applyLimiter {
+		r.Limiter <- struct{}{}
+	}
+
+	var result reflect.Value
+	var err *errors.QueryError
+
+	traceCtx, finish := r.Tracer.TraceField(ctx, f.field.TraceLabel, f.field.TypeName, f.field.Name, !f.field.Async, f.field.Args)
+	defer func() {
+		finish(err)
+	}()
+
+	err = func() (err *errors.QueryError) {
+		defer func() {
+			if panicValue := recover(); panicValue != nil {
+				r.Logger.LogPanic(ctx, panicValue)
+				err = r.PanicHandler.MakePanicError(ctx, panicValue)
+				err.Path = path.toSlice()
+			}
+		}()
+
+		if f.field.FixedResult.IsValid() {
+			result = f.field.FixedResult
+			return nil
+		}
+
+		if err := traceCtx.Err(); err != nil {
+			return errors.Errorf("%s", err) // don't execute any more resolvers if context got cancelled
+		}
+
+		res := f.resolver
+		if f.field.UseMethodResolver() {
+			var in []reflect.Value
+			if f.field.HasContext {
+				in = append(in, reflect.ValueOf(traceCtx))
+			}
+			if f.field.ArgsPacker != nil {
+				in = append(in, f.field.PackedArgs)
+			}
+			callOut := res.Method(f.field.MethodIndex).Call(in)
+			result = callOut[0]
+			if f.field.HasError && !callOut[1].IsNil() {
+				resolverErr := callOut[1].Interface().(error)
+				err := errors.Errorf("%s", resolverErr)
+				err.Path = path.toSlice()
+				err.ResolverError = resolverErr
+				if ex, ok := callOut[1].Interface().(extensionser); ok {
+					err.Extensions = ex.Extensions()
+				}
+				return err
+			}
+		} else {
+			// TODO extract out unwrapping ptr logic to a common place
+			if res.Kind() == reflect.Ptr {
+				res = res.Elem()
+			}
+			result = res.FieldByIndex(f.field.FieldIndex)
+		}
+		return nil
+	}()
+
+	if applyLimiter {
+		<-r.Limiter
+	}
+
+	if err != nil {
+		// If an error occurred while resolving a field, it should be treated as though the field
+		// returned null, and an error must be added to the "errors" list in the response.
+		r.AddError(err)
+		f.out.WriteString("null")
+		return
+	}
+
+	r.execSelectionSet(traceCtx, f.sels, f.field.Type, path, s, result, f.out)
+}
+
+func (r *Request) execSelectionSet(ctx context.Context, sels []selected.Selection, typ types.Type, path *pathSegment, s *resolvable.Schema, resolver reflect.Value, out *bytes.Buffer) {
+	t, nonNull := unwrapNonNull(typ)
+
+	// a reflect.Value of a nil interface will show up as an Invalid value
+	if resolver.Kind() == reflect.Invalid || ((resolver.Kind() == reflect.Ptr || resolver.Kind() == reflect.Interface) && resolver.IsNil()) {
+		// If a field of a non-null type resolves to null (either because the
+		// function to resolve the field returned null or because an error occurred),
+		// add an error to the "errors" list in the response.
+		if nonNull {
+			err := errors.Errorf("graphql: got nil for non-null %q", t)
+			err.Path = path.toSlice()
+			r.AddError(err)
+		}
+		out.WriteString("null")
+		return
+	}
+
+	switch t.(type) {
+	case *types.ObjectTypeDefinition, *types.InterfaceTypeDefinition, *types.Union:
+		r.execSelections(ctx, sels, path, s, resolver, out, false)
+		return
+	}
+
+	// Any pointers or interfaces at this point should be non-nil, so we can get the actual value of them
+	// for serialization
+	if resolver.Kind() == reflect.Ptr || resolver.Kind() == reflect.Interface {
+		resolver = resolver.Elem()
+	}
+
+	switch t := t.(type) {
+	case *types.List:
+		r.execList(ctx, sels, t, path, s, resolver, out)
+
+	case *types.ScalarTypeDefinition:
+		v := resolver.Interface()
+		data, err := json.Marshal(v)
+		if err != nil {
+			panic(errors.Errorf("could not marshal %v: %s", v, err))
+		}
+		out.Write(data)
+
+	case *types.EnumTypeDefinition:
+		var stringer fmt.Stringer = resolver
+		if s, ok := resolver.Interface().(fmt.Stringer); ok {
+			stringer = s
+		}
+		name := stringer.String()
+		var valid bool
+		for _, v := range t.EnumValuesDefinition {
+			if v.EnumValue == name {
+				valid = true
+				break
+			}
+		}
+		if !valid {
+			err := errors.Errorf("Invalid value %s.\nExpected type %s, found %s.", name, t.Name, name)
+			err.Path = path.toSlice()
+			r.AddError(err)
+			out.WriteString("null")
+			return
+		}
+		out.WriteByte('"')
+		out.WriteString(name)
+		out.WriteByte('"')
+
+	default:
+		panic("unreachable")
+	}
+}
+
+func (r *Request) execList(ctx context.Context, sels []selected.Selection, typ *types.List, path *pathSegment, s *resolvable.Schema, resolver reflect.Value, out *bytes.Buffer) {
+	l := resolver.Len()
+	entryouts := make([]bytes.Buffer, l)
+
+	if selected.HasAsyncSel(sels) {
+		// Limit the number of concurrent goroutines spawned as it can lead to large
+		// memory spikes for large lists.
+		concurrency := cap(r.Limiter)
+		sem := make(chan struct{}, concurrency)
+		for i := 0; i < l; i++ {
+			sem <- struct{}{}
+			go func(i int) {
+				defer func() { <-sem }()
+				defer r.handlePanic(ctx)
+				r.execSelectionSet(ctx, sels, typ.OfType, &pathSegment{path, i}, s, resolver.Index(i), &entryouts[i])
+			}(i)
+		}
+		for i := 0; i < concurrency; i++ {
+			sem <- struct{}{}
+		}
+	} else {
+		for i := 0; i < l; i++ {
+			r.execSelectionSet(ctx, sels, typ.OfType, &pathSegment{path, i}, s, resolver.Index(i), &entryouts[i])
+		}
+	}
+
+	_, listOfNonNull := typ.OfType.(*types.NonNull)
+
+	out.WriteByte('[')
+	for i, entryout := range entryouts {
+		// If the list wraps a non-null type and one of the list elements
+		// resolves to null, then the entire list resolves to null.
+		if listOfNonNull && resolvedToNull(&entryout) {
+			out.Reset()
+			out.WriteString("null")
+			return
+		}
+
+		if i > 0 {
+			out.WriteByte(',')
+		}
+		out.Write(entryout.Bytes())
+	}
+	out.WriteByte(']')
+}
+
+func unwrapNonNull(t types.Type) (types.Type, bool) {
+	if nn, ok := t.(*types.NonNull); ok {
+		return nn.OfType, true
+	}
+	return t, false
+}
+
+type pathSegment struct {
+	parent *pathSegment
+	value  interface{}
+}
+
+func (p *pathSegment) toSlice() []interface{} {
+	if p == nil {
+		return nil
+	}
+	return append(p.parent.toSlice(), p.value)
+}
diff --git a/vendor/github.com/graph-gophers/graphql-go/internal/exec/packer/packer.go b/vendor/github.com/graph-gophers/graphql-go/internal/exec/packer/packer.go
new file mode 100644
index 00000000..c0bb7dc9
--- /dev/null
+++ b/vendor/github.com/graph-gophers/graphql-go/internal/exec/packer/packer.go
@@ -0,0 +1,390 @@
+package packer
+
+import (
+	"fmt"
+	"math"
+	"reflect"
+	"strings"
+
+	"github.com/graph-gophers/graphql-go/decode"
+	"github.com/graph-gophers/graphql-go/errors"
+	"github.com/graph-gophers/graphql-go/types"
+)
+
+type packer interface {
+	Pack(value interface{}) (reflect.Value, error)
+}
+
+type Builder struct {
+	packerMap     map[typePair]*packerMapEntry
+	structPackers []*StructPacker
+}
+
+type typePair struct {
+	graphQLType  types.Type
+	resolverType reflect.Type
+}
+
+type packerMapEntry struct {
+	packer  packer
+	targets []*packer
+}
+
+func NewBuilder() *Builder {
+	return &Builder{
+		packerMap: make(map[typePair]*packerMapEntry),
+	}
+}
+
+func (b *Builder) Finish() error {
+	for _, entry := range b.packerMap {
+		for _, target := range entry.targets {
+			*target = entry.packer
+		}
+	}
+
+	for _, p := range b.structPackers {
+		p.defaultStruct = reflect.New(p.structType).Elem()
+		for _, f := range p.fields {
+			if defaultVal := f.field.Default; defaultVal != nil {
+				v, err := f.fieldPacker.Pack(defaultVal.Deserialize(nil))
+				if err != nil {
+					return err
+				}
+				p.defaultStruct.FieldByIndex(f.fieldIndex).Set(v)
+			}
+		}
+	}
+
+	return nil
+}
+
+func (b *Builder) assignPacker(target *packer, schemaType types.Type, reflectType reflect.Type) error {
+	k := typePair{schemaType, reflectType}
+	ref, ok := b.packerMap[k]
+	if !ok {
+		ref = &packerMapEntry{}
+		b.packerMap[k] = ref
+		var err error
+		ref.packer, err = b.makePacker(schemaType, reflectType)
+		if err != nil {
+			return err
+		}
+	}
+	ref.targets = append(ref.targets, target)
+	return nil
+}
+
+func (b *Builder) makePacker(schemaType types.Type, reflectType reflect.Type) (packer, error) {
+	t, nonNull := unwrapNonNull(schemaType)
+	if !nonNull {
+		if reflectType.Kind() == reflect.Ptr {
+			elemType := reflectType.Elem()
+			addPtr := true
+			if _, ok := t.(*types.InputObject); ok {
+				elemType = reflectType // keep pointer for input objects
+				addPtr = false
+			}
+			elem, err := b.makeNonNullPacker(t, elemType)
+			if err != nil {
+				return nil, err
+			}
+			return &nullPacker{
+				elemPacker: elem,
+				valueType:  reflectType,
+				addPtr:     addPtr,
+			}, nil
+		} else if isNullable(reflectType) {
+			elemType := reflectType
+			addPtr := false
+			elem, err := b.makeNonNullPacker(t, elemType)
+			if err != nil {
+				return nil, err
+			}
+			return &nullPacker{
+				elemPacker: elem,
+				valueType:  reflectType,
+				addPtr:     addPtr,
+			}, nil
+		} else {
+			return nil, fmt.Errorf("%s is not a pointer or a nullable type", reflectType)
+		}
+	}
+
+	return b.makeNonNullPacker(t, reflectType)
+}
+
+func (b *Builder) makeNonNullPacker(schemaType types.Type, reflectType reflect.Type) (packer, error) {
+	if u, ok := reflect.New(reflectType).Interface().(decode.Unmarshaler); ok {
+		if !u.ImplementsGraphQLType(schemaType.String()) {
+			return nil, fmt.Errorf("can not unmarshal %s into %s", schemaType, reflectType)
+		}
+		return &unmarshalerPacker{
+			ValueType: reflectType,
+		}, nil
+	}
+
+	switch t := schemaType.(type) {
+	case *types.ScalarTypeDefinition:
+		return &ValuePacker{
+			ValueType: reflectType,
+		}, nil
+
+	case *types.EnumTypeDefinition:
+		if reflectType.Kind() != reflect.String {
+			return nil, fmt.Errorf("wrong type, expected %s", reflect.String)
+		}
+		return &ValuePacker{
+			ValueType: reflectType,
+		}, nil
+
+	case *types.InputObject:
+		e, err := b.MakeStructPacker(t.Values, reflectType)
+		if err != nil {
+			return nil, err
+		}
+		return e, nil
+
+	case *types.List:
+		if reflectType.Kind() != reflect.Slice {
+			return nil, fmt.Errorf("expected slice, got %s", reflectType)
+		}
+		p := &listPacker{
+			sliceType: reflectType,
+		}
+		if err := b.assignPacker(&p.elem, t.OfType, reflectType.Elem()); err != nil {
+			return nil, err
+		}
+		return p, nil
+
+	case *types.ObjectTypeDefinition, *types.InterfaceTypeDefinition, *types.Union:
+		return nil, fmt.Errorf("type of kind %s can not be used as input", t.Kind())
+
+	default:
+		panic("unreachable")
+	}
+}
+
+func (b *Builder) MakeStructPacker(values []*types.InputValueDefinition, typ reflect.Type) (*StructPacker, error) {
+	structType := typ
+	usePtr := false
+	if typ.Kind() == reflect.Ptr {
+		structType = typ.Elem()
+		usePtr = true
+	}
+	if structType.Kind() != reflect.Struct {
+		return nil, fmt.Errorf("expected struct or pointer to struct, got %s (hint: missing `args struct { ... }` wrapper for field arguments?)", typ)
+	}
+
+	var fields []*structPackerField
+	for _, v := range values {
+		fe := &structPackerField{field: v}
+		fx := func(n string) bool {
+			return strings.EqualFold(stripUnderscore(n), stripUnderscore(v.Name.Name))
+		}
+
+		sf, ok := structType.FieldByNameFunc(fx)
+		if !ok {
+			return nil, fmt.Errorf("%s does not define field %q (hint: missing `args struct { ... }` wrapper for field arguments, or missing field on input struct)", typ, v.Name.Name)
+		}
+		if sf.PkgPath != "" {
+			return nil, fmt.Errorf("field %q must be exported", sf.Name)
+		}
+		fe.fieldIndex = sf.Index
+
+		ft := v.Type
+		if v.Default != nil {
+			ft, _ = unwrapNonNull(ft)
+			ft = &types.NonNull{OfType: ft}
+		}
+
+		if err := b.assignPacker(&fe.fieldPacker, ft, sf.Type); err != nil {
+			return nil, fmt.Errorf("field %q: %s", sf.Name, err)
+		}
+
+		fields = append(fields, fe)
+	}
+
+	p := &StructPacker{
+		structType: structType,
+		usePtr:     usePtr,
+		fields:     fields,
+	}
+	b.structPackers = append(b.structPackers, p)
+	return p, nil
+}
+
+type StructPacker struct {
+	structType    reflect.Type
+	usePtr        bool
+	defaultStruct reflect.Value
+	fields        []*structPackerField
+}
+
+type structPackerField struct {
+	field       *types.InputValueDefinition
+	fieldIndex  []int
+	fieldPacker packer
+}
+
+func (p *StructPacker) Pack(value interface{}) (reflect.Value, error) {
+	if value == nil {
+		return reflect.Value{}, errors.Errorf("got null for non-null")
+	}
+
+	values := value.(map[string]interface{})
+	v := reflect.New(p.structType)
+	v.Elem().Set(p.defaultStruct)
+	for _, f := range p.fields {
+		if value, ok := values[f.field.Name.Name]; ok {
+			packed, err := f.fieldPacker.Pack(value)
+			if err != nil {
+				return reflect.Value{}, err
+			}
+			v.Elem().FieldByIndex(f.fieldIndex).Set(packed)
+		}
+	}
+	if !p.usePtr {
+		return v.Elem(), nil
+	}
+	return v, nil
+}
+
+type listPacker struct {
+	sliceType reflect.Type
+	elem      packer
+}
+
+func (e *listPacker) Pack(value interface{}) (reflect.Value, error) {
+	list, ok := value.([]interface{})
+	if !ok {
+		list = []interface{}{value}
+	}
+
+	v := reflect.MakeSlice(e.sliceType, len(list), len(list))
+	for i := range list {
+		packed, err := e.elem.Pack(list[i])
+		if err != nil {
+			return reflect.Value{}, err
+		}
+		v.Index(i).Set(packed)
+	}
+	return v, nil
+}
+
+type nullPacker struct {
+	elemPacker packer
+	valueType  reflect.Type
+	addPtr     bool
+}
+
+func (p *nullPacker) Pack(value interface{}) (reflect.Value, error) {
+	if value == nil && !isNullable(p.valueType) {
+		return reflect.Zero(p.valueType), nil
+	}
+
+	v, err := p.elemPacker.Pack(value)
+	if err != nil {
+		return reflect.Value{}, err
+	}
+
+	if p.addPtr {
+		ptr := reflect.New(p.valueType.Elem())
+		ptr.Elem().Set(v)
+		return ptr, nil
+	}
+
+	return v, nil
+}
+
+type ValuePacker struct {
+	ValueType reflect.Type
+}
+
+func (p *ValuePacker) Pack(value interface{}) (reflect.Value, error) {
+	if value == nil {
+		return reflect.Value{}, errors.Errorf("got null for non-null")
+	}
+
+	coerced, err := unmarshalInput(p.ValueType, value)
+	if err != nil {
+		return reflect.Value{}, fmt.Errorf("could not unmarshal %#v (%T) into %s: %s", value, value, p.ValueType, err)
+	}
+	return reflect.ValueOf(coerced), nil
+}
+
+type unmarshalerPacker struct {
+	ValueType reflect.Type
+}
+
+func (p *unmarshalerPacker) Pack(value interface{}) (reflect.Value, error) {
+	if value == nil && !isNullable(p.ValueType) {
+		return reflect.Value{}, errors.Errorf("got null for non-null")
+	}
+
+	v := reflect.New(p.ValueType)
+	if err := v.Interface().(decode.Unmarshaler).UnmarshalGraphQL(value); err != nil {
+		return reflect.Value{}, err
+	}
+	return v.Elem(), nil
+}
+
+func unmarshalInput(typ reflect.Type, input interface{}) (interface{}, error) {
+	if reflect.TypeOf(input) == typ {
+		return input, nil
+	}
+
+	switch typ.Kind() {
+	case reflect.Int32:
+		switch input := input.(type) {
+		case int:
+			if input < math.MinInt32 || input > math.MaxInt32 {
+				return nil, fmt.Errorf("not a 32-bit integer")
+			}
+			return int32(input), nil
+		case float64:
+			coerced := int32(input)
+			if input < math.MinInt32 || input > math.MaxInt32 || float64(coerced) != input {
+				return nil, fmt.Errorf("not a 32-bit integer")
+			}
+			return coerced, nil
+		}
+
+	case reflect.Float64:
+		switch input := input.(type) {
+		case int32:
+			return float64(input), nil
+		case int:
+			return float64(input), nil
+		}
+
+	case reflect.String:
+		if reflect.TypeOf(input).ConvertibleTo(typ) {
+			return reflect.ValueOf(input).Convert(typ).Interface(), nil
+		}
+	}
+
+	return nil, fmt.Errorf("incompatible type")
+}
+
+func unwrapNonNull(t types.Type) (types.Type, bool) {
+	if nn, ok := t.(*types.NonNull); ok {
+		return nn.OfType, true
+	}
+	return t, false
+}
+
+func stripUnderscore(s string) string {
+	return strings.Replace(s, "_", "", -1)
+}
+
+// NullUnmarshaller is an unmarshaller that can handle a nil input
+type NullUnmarshaller interface {
+	decode.Unmarshaler
+	Nullable()
+}
+
+func isNullable(t reflect.Type) bool {
+	_, ok := reflect.New(t).Interface().(NullUnmarshaller)
+	return ok
+}
diff --git a/vendor/github.com/graph-gophers/graphql-go/internal/exec/resolvable/meta.go b/vendor/github.com/graph-gophers/graphql-go/internal/exec/resolvable/meta.go
new file mode 100644
index 00000000..02d5e262
--- /dev/null
+++ b/vendor/github.com/graph-gophers/graphql-go/internal/exec/resolvable/meta.go
@@ -0,0 +1,70 @@
+package resolvable
+
+import (
+	"reflect"
+
+	"github.com/graph-gophers/graphql-go/introspection"
+	"github.com/graph-gophers/graphql-go/types"
+)
+
+// Meta defines the details of the metadata schema for introspection.
+type Meta struct {
+	FieldSchema   Field
+	FieldType     Field
+	FieldTypename Field
+	Schema        *Object
+	Type          *Object
+}
+
+func newMeta(s *types.Schema) *Meta {
+	var err error
+	b := newBuilder(s)
+
+	metaSchema := s.Types["__Schema"].(*types.ObjectTypeDefinition)
+	so, err := b.makeObjectExec(metaSchema.Name, metaSchema.Fields, nil, false, reflect.TypeOf(&introspection.Schema{}))
+	if err != nil {
+		panic(err)
+	}
+
+	metaType := s.Types["__Type"].(*types.ObjectTypeDefinition)
+	t, err := b.makeObjectExec(metaType.Name, metaType.Fields, nil, false, reflect.TypeOf(&introspection.Type{}))
+	if err != nil {
+		panic(err)
+	}
+
+	if err := b.finish(); err != nil {
+		panic(err)
+	}
+
+	fieldTypename := Field{
+		FieldDefinition: types.FieldDefinition{
+			Name: "__typename",
+			Type: &types.NonNull{OfType: s.Types["String"]},
+		},
+		TraceLabel: "GraphQL field: __typename",
+	}
+
+	fieldSchema := Field{
+		FieldDefinition: types.FieldDefinition{
+			Name: "__schema",
+			Type: s.Types["__Schema"],
+		},
+		TraceLabel: "GraphQL field: __schema",
+	}
+
+	fieldType := Field{
+		FieldDefinition: types.FieldDefinition{
+			Name: "__type",
+			Type: s.Types["__Type"],
+		},
+		TraceLabel: "GraphQL field: __type",
+	}
+
+	return &Meta{
+		FieldSchema:   fieldSchema,
+		FieldTypename: fieldTypename,
+		FieldType:     fieldType,
+		Schema:        so,
+		Type:          t,
+	}
+}
diff --git a/vendor/github.com/graph-gophers/graphql-go/internal/exec/resolvable/resolvable.go b/vendor/github.com/graph-gophers/graphql-go/internal/exec/resolvable/resolvable.go
new file mode 100644
index 00000000..3410f557
--- /dev/null
+++ b/vendor/github.com/graph-gophers/graphql-go/internal/exec/resolvable/resolvable.go
@@ -0,0 +1,453 @@
+package resolvable
+
+import (
+	"context"
+	"fmt"
+	"reflect"
+	"strings"
+
+	"github.com/graph-gophers/graphql-go/decode"
+	"github.com/graph-gophers/graphql-go/internal/exec/packer"
+	"github.com/graph-gophers/graphql-go/types"
+)
+
+type Schema struct {
+	*Meta
+	types.Schema
+	Query        Resolvable
+	Mutation     Resolvable
+	Subscription Resolvable
+	Resolver     reflect.Value
+}
+
+type Resolvable interface {
+	isResolvable()
+}
+
+type Object struct {
+	Name           string
+	Fields         map[string]*Field
+	TypeAssertions map[string]*TypeAssertion
+}
+
+type Field struct {
+	types.FieldDefinition
+	TypeName    string
+	MethodIndex int
+	FieldIndex  []int
+	HasContext  bool
+	HasError    bool
+	ArgsPacker  *packer.StructPacker
+	ValueExec   Resolvable
+	TraceLabel  string
+}
+
+func (f *Field) UseMethodResolver() bool {
+	return len(f.FieldIndex) == 0
+}
+
+type TypeAssertion struct {
+	MethodIndex int
+	TypeExec    Resolvable
+}
+
+type List struct {
+	Elem Resolvable
+}
+
+type Scalar struct{}
+
+func (*Object) isResolvable() {}
+func (*List) isResolvable()   {}
+func (*Scalar) isResolvable() {}
+
+func ApplyResolver(s *types.Schema, resolver interface{}) (*Schema, error) {
+	if resolver == nil {
+		return &Schema{Meta: newMeta(s), Schema: *s}, nil
+	}
+
+	b := newBuilder(s)
+
+	var query, mutation, subscription Resolvable
+
+	if t, ok := s.EntryPoints["query"]; ok {
+		if err := b.assignExec(&query, t, reflect.TypeOf(resolver)); err != nil {
+			return nil, err
+		}
+	}
+
+	if t, ok := s.EntryPoints["mutation"]; ok {
+		if err := b.assignExec(&mutation, t, reflect.TypeOf(resolver)); err != nil {
+			return nil, err
+		}
+	}
+
+	if t, ok := s.EntryPoints["subscription"]; ok {
+		if err := b.assignExec(&subscription, t, reflect.TypeOf(resolver)); err != nil {
+			return nil, err
+		}
+	}
+
+	if err := b.finish(); err != nil {
+		return nil, err
+	}
+
+	return &Schema{
+		Meta:         newMeta(s),
+		Schema:       *s,
+		Resolver:     reflect.ValueOf(resolver),
+		Query:        query,
+		Mutation:     mutation,
+		Subscription: subscription,
+	}, nil
+}
+
+type execBuilder struct {
+	schema        *types.Schema
+	resMap        map[typePair]*resMapEntry
+	packerBuilder *packer.Builder
+}
+
+type typePair struct {
+	graphQLType  types.Type
+	resolverType reflect.Type
+}
+
+type resMapEntry struct {
+	exec    Resolvable
+	targets []*Resolvable
+}
+
+func newBuilder(s *types.Schema) *execBuilder {
+	return &execBuilder{
+		schema:        s,
+		resMap:        make(map[typePair]*resMapEntry),
+		packerBuilder: packer.NewBuilder(),
+	}
+}
+
+func (b *execBuilder) finish() error {
+	for _, entry := range b.resMap {
+		for _, target := range entry.targets {
+			*target = entry.exec
+		}
+	}
+
+	return b.packerBuilder.Finish()
+}
+
+func (b *execBuilder) assignExec(target *Resolvable, t types.Type, resolverType reflect.Type) error {
+	k := typePair{t, resolverType}
+	ref, ok := b.resMap[k]
+	if !ok {
+		ref = &resMapEntry{}
+		b.resMap[k] = ref
+		var err error
+		ref.exec, err = b.makeExec(t, resolverType)
+		if err != nil {
+			return err
+		}
+	}
+	ref.targets = append(ref.targets, target)
+	return nil
+}
+
+func (b *execBuilder) makeExec(t types.Type, resolverType reflect.Type) (Resolvable, error) {
+	var nonNull bool
+	t, nonNull = unwrapNonNull(t)
+
+	switch t := t.(type) {
+	case *types.ObjectTypeDefinition:
+		return b.makeObjectExec(t.Name, t.Fields, nil, nonNull, resolverType)
+
+	case *types.InterfaceTypeDefinition:
+		return b.makeObjectExec(t.Name, t.Fields, t.PossibleTypes, nonNull, resolverType)
+
+	case *types.Union:
+		return b.makeObjectExec(t.Name, nil, t.UnionMemberTypes, nonNull, resolverType)
+	}
+
+	if !nonNull {
+		if resolverType.Kind() != reflect.Ptr {
+			return nil, fmt.Errorf("%s is not a pointer", resolverType)
+		}
+		resolverType = resolverType.Elem()
+	}
+
+	switch t := t.(type) {
+	case *types.ScalarTypeDefinition:
+		return makeScalarExec(t, resolverType)
+
+	case *types.EnumTypeDefinition:
+		return &Scalar{}, nil
+
+	case *types.List:
+		if resolverType.Kind() != reflect.Slice {
+			return nil, fmt.Errorf("%s is not a slice", resolverType)
+		}
+		e := &List{}
+		if err := b.assignExec(&e.Elem, t.OfType, resolverType.Elem()); err != nil {
+			return nil, err
+		}
+		return e, nil
+
+	default:
+		panic("invalid type: " + t.String())
+	}
+}
+
+func makeScalarExec(t *types.ScalarTypeDefinition, resolverType reflect.Type) (Resolvable, error) {
+	implementsType := false
+	switch r := reflect.New(resolverType).Interface().(type) {
+	case *int32:
+		implementsType = t.Name == "Int"
+	case *float64:
+		implementsType = t.Name == "Float"
+	case *string:
+		implementsType = t.Name == "String"
+	case *bool:
+		implementsType = t.Name == "Boolean"
+	case decode.Unmarshaler:
+		implementsType = r.ImplementsGraphQLType(t.Name)
+	}
+
+	if !implementsType {
+		return nil, fmt.Errorf("can not use %s as %s", resolverType, t.Name)
+	}
+	return &Scalar{}, nil
+}
+
+func (b *execBuilder) makeObjectExec(typeName string, fields types.FieldsDefinition, possibleTypes []*types.ObjectTypeDefinition,
+	nonNull bool, resolverType reflect.Type) (*Object, error) {
+	if !nonNull {
+		if resolverType.Kind() != reflect.Ptr && resolverType.Kind() != reflect.Interface {
+			return nil, fmt.Errorf("%s is not a pointer or interface", resolverType)
+		}
+	}
+
+	methodHasReceiver := resolverType.Kind() != reflect.Interface
+
+	Fields := make(map[string]*Field)
+	rt := unwrapPtr(resolverType)
+	fieldsCount := fieldCount(rt, map[string]int{})
+	for _, f := range fields {
+		var fieldIndex []int
+		methodIndex := findMethod(resolverType, f.Name)
+		if b.schema.UseFieldResolvers && methodIndex == -1 {
+			if fieldsCount[strings.ToLower(stripUnderscore(f.Name))] > 1 {
+				return nil, fmt.Errorf("%s does not resolve %q: ambiguous field %q", resolverType, typeName, f.Name)
+			}
+			fieldIndex = findField(rt, f.Name, []int{})
+		}
+		if methodIndex == -1 && len(fieldIndex) == 0 {
+			hint := ""
+			if findMethod(reflect.PtrTo(resolverType), f.Name) != -1 {
+				hint = " (hint: the method exists on the pointer type)"
+			}
+			return nil, fmt.Errorf("%s does not resolve %q: missing method for field %q%s", resolverType, typeName, f.Name, hint)
+		}
+
+		var m reflect.Method
+		var sf reflect.StructField
+		if methodIndex != -1 {
+			m = resolverType.Method(methodIndex)
+		} else {
+			sf = rt.FieldByIndex(fieldIndex)
+		}
+		fe, err := b.makeFieldExec(typeName, f, m, sf, methodIndex, fieldIndex, methodHasReceiver)
+		if err != nil {
+			var resolverName string
+			if methodIndex != -1 {
+				resolverName = m.Name
+			} else {
+				resolverName = sf.Name
+			}
+			return nil, fmt.Errorf("%s\n\tused by (%s).%s", err, resolverType, resolverName)
+		}
+		Fields[f.Name] = fe
+	}
+
+	// Check type assertions when
+	//	1) using method resolvers
+	//	2) Or resolver is not an interface type
+	typeAssertions := make(map[string]*TypeAssertion)
+	if !b.schema.UseFieldResolvers || resolverType.Kind() != reflect.Interface {
+		for _, impl := range possibleTypes {
+			methodIndex := findMethod(resolverType, "To"+impl.Name)
+			if methodIndex == -1 {
+				return nil, fmt.Errorf("%s does not resolve %q: missing method %q to convert to %q", resolverType, typeName, "To"+impl.Name, impl.Name)
+			}
+			if resolverType.Method(methodIndex).Type.NumOut() != 2 {
+				return nil, fmt.Errorf("%s does not resolve %q: method %q should return a value and a bool indicating success", resolverType, typeName, "To"+impl.Name)
+			}
+			a := &TypeAssertion{
+				MethodIndex: methodIndex,
+			}
+			if err := b.assignExec(&a.TypeExec, impl, resolverType.Method(methodIndex).Type.Out(0)); err != nil {
+				return nil, err
+			}
+			typeAssertions[impl.Name] = a
+		}
+	}
+
+	return &Object{
+		Name:           typeName,
+		Fields:         Fields,
+		TypeAssertions: typeAssertions,
+	}, nil
+}
+
+var contextType = reflect.TypeOf((*context.Context)(nil)).Elem()
+var errorType = reflect.TypeOf((*error)(nil)).Elem()
+
+func (b *execBuilder) makeFieldExec(typeName string, f *types.FieldDefinition, m reflect.Method, sf reflect.StructField,
+	methodIndex int, fieldIndex []int, methodHasReceiver bool) (*Field, error) {
+
+	var argsPacker *packer.StructPacker
+	var hasError bool
+	var hasContext bool
+
+	// Validate resolver method only when there is one
+	if methodIndex != -1 {
+		in := make([]reflect.Type, m.Type.NumIn())
+		for i := range in {
+			in[i] = m.Type.In(i)
+		}
+		if methodHasReceiver {
+			in = in[1:] // first parameter is receiver
+		}
+
+		hasContext = len(in) > 0 && in[0] == contextType
+		if hasContext {
+			in = in[1:]
+		}
+
+		if len(f.Arguments) > 0 {
+			if len(in) == 0 {
+				return nil, fmt.Errorf("must have parameter for field arguments")
+			}
+			var err error
+			argsPacker, err = b.packerBuilder.MakeStructPacker(f.Arguments, in[0])
+			if err != nil {
+				return nil, err
+			}
+			in = in[1:]
+		}
+
+		if len(in) > 0 {
+			return nil, fmt.Errorf("too many parameters")
+		}
+
+		maxNumOfReturns := 2
+		if m.Type.NumOut() < maxNumOfReturns-1 {
+			return nil, fmt.Errorf("too few return values")
+		}
+
+		if m.Type.NumOut() > maxNumOfReturns {
+			return nil, fmt.Errorf("too many return values")
+		}
+
+		hasError = m.Type.NumOut() == maxNumOfReturns
+		if hasError {
+			if m.Type.Out(maxNumOfReturns-1) != errorType {
+				return nil, fmt.Errorf(`must have "error" as its last return value`)
+			}
+		}
+	}
+
+	fe := &Field{
+		FieldDefinition: *f,
+		TypeName:        typeName,
+		MethodIndex:     methodIndex,
+		FieldIndex:      fieldIndex,
+		HasContext:      hasContext,
+		ArgsPacker:      argsPacker,
+		HasError:        hasError,
+		TraceLabel:      fmt.Sprintf("GraphQL field: %s.%s", typeName, f.Name),
+	}
+
+	var out reflect.Type
+	if methodIndex != -1 {
+		out = m.Type.Out(0)
+		sub, ok := b.schema.EntryPoints["subscription"]
+		if ok && typeName == sub.TypeName() && out.Kind() == reflect.Chan {
+			out = m.Type.Out(0).Elem()
+		}
+	} else {
+		out = sf.Type
+	}
+	if err := b.assignExec(&fe.ValueExec, f.Type, out); err != nil {
+		return nil, err
+	}
+
+	return fe, nil
+}
+
+func findMethod(t reflect.Type, name string) int {
+	for i := 0; i < t.NumMethod(); i++ {
+		if strings.EqualFold(stripUnderscore(name), stripUnderscore(t.Method(i).Name)) {
+			return i
+		}
+	}
+	return -1
+}
+
+func findField(t reflect.Type, name string, index []int) []int {
+	for i := 0; i < t.NumField(); i++ {
+		field := t.Field(i)
+
+		if field.Type.Kind() == reflect.Struct && field.Anonymous {
+			newIndex := findField(field.Type, name, []int{i})
+			if len(newIndex) > 1 {
+				return append(index, newIndex...)
+			}
+		}
+
+		if strings.EqualFold(stripUnderscore(name), stripUnderscore(field.Name)) {
+			return append(index, i)
+		}
+	}
+
+	return index
+}
+
+// fieldCount helps resolve ambiguity when more than one embedded struct contains fields with the same name.
+func fieldCount(t reflect.Type, count map[string]int) map[string]int {
+	if t.Kind() != reflect.Struct {
+		return nil
+	}
+
+	for i := 0; i < t.NumField(); i++ {
+		field := t.Field(i)
+		fieldName := strings.ToLower(stripUnderscore(field.Name))
+
+		if field.Type.Kind() == reflect.Struct && field.Anonymous {
+			count = fieldCount(field.Type, count)
+		} else {
+			if _, ok := count[fieldName]; !ok {
+				count[fieldName] = 0
+			}
+			count[fieldName]++
+		}
+	}
+
+	return count
+}
+
+func unwrapNonNull(t types.Type) (types.Type, bool) {
+	if nn, ok := t.(*types.NonNull); ok {
+		return nn.OfType, true
+	}
+	return t, false
+}
+
+func stripUnderscore(s string) string {
+	return strings.Replace(s, "_", "", -1)
+}
+
+func unwrapPtr(t reflect.Type) reflect.Type {
+	if t.Kind() == reflect.Ptr {
+		return t.Elem()
+	}
+	return t
+}
diff --git a/vendor/github.com/graph-gophers/graphql-go/internal/exec/selected/selected.go b/vendor/github.com/graph-gophers/graphql-go/internal/exec/selected/selected.go
new file mode 100644
index 00000000..9b96d2b6
--- /dev/null
+++ b/vendor/github.com/graph-gophers/graphql-go/internal/exec/selected/selected.go
@@ -0,0 +1,269 @@
+package selected
+
+import (
+	"fmt"
+	"reflect"
+	"sync"
+
+	"github.com/graph-gophers/graphql-go/errors"
+	"github.com/graph-gophers/graphql-go/internal/exec/packer"
+	"github.com/graph-gophers/graphql-go/internal/exec/resolvable"
+	"github.com/graph-gophers/graphql-go/internal/query"
+	"github.com/graph-gophers/graphql-go/introspection"
+	"github.com/graph-gophers/graphql-go/types"
+)
+
+type Request struct {
+	Schema               *types.Schema
+	Doc                  *types.ExecutableDefinition
+	Vars                 map[string]interface{}
+	Mu                   sync.Mutex
+	Errs                 []*errors.QueryError
+	DisableIntrospection bool
+}
+
+func (r *Request) AddError(err *errors.QueryError) {
+	r.Mu.Lock()
+	r.Errs = append(r.Errs, err)
+	r.Mu.Unlock()
+}
+
+func ApplyOperation(r *Request, s *resolvable.Schema, op *types.OperationDefinition) []Selection {
+	var obj *resolvable.Object
+	switch op.Type {
+	case query.Query:
+		obj = s.Query.(*resolvable.Object)
+	case query.Mutation:
+		obj = s.Mutation.(*resolvable.Object)
+	case query.Subscription:
+		obj = s.Subscription.(*resolvable.Object)
+	}
+	return applySelectionSet(r, s, obj, op.Selections)
+}
+
+type Selection interface {
+	isSelection()
+}
+
+type SchemaField struct {
+	resolvable.Field
+	Alias       string
+	Args        map[string]interface{}
+	PackedArgs  reflect.Value
+	Sels        []Selection
+	Async       bool
+	FixedResult reflect.Value
+}
+
+type TypeAssertion struct {
+	resolvable.TypeAssertion
+	Sels []Selection
+}
+
+type TypenameField struct {
+	resolvable.Object
+	Alias string
+}
+
+func (*SchemaField) isSelection()   {}
+func (*TypeAssertion) isSelection() {}
+func (*TypenameField) isSelection() {}
+
+func applySelectionSet(r *Request, s *resolvable.Schema, e *resolvable.Object, sels []types.Selection) (flattenedSels []Selection) {
+	for _, sel := range sels {
+		switch sel := sel.(type) {
+		case *types.Field:
+			field := sel
+			if skipByDirective(r, field.Directives) {
+				continue
+			}
+
+			switch field.Name.Name {
+			case "__typename":
+				// __typename is available even though r.DisableIntrospection == true
+				// because it is necessary when using union types and interfaces: https://graphql.org/learn/schema/#union-types
+				flattenedSels = append(flattenedSels, &TypenameField{
+					Object: *e,
+					Alias:  field.Alias.Name,
+				})
+
+			case "__schema":
+				if !r.DisableIntrospection {
+					flattenedSels = append(flattenedSels, &SchemaField{
+						Field:       s.Meta.FieldSchema,
+						Alias:       field.Alias.Name,
+						Sels:        applySelectionSet(r, s, s.Meta.Schema, field.SelectionSet),
+						Async:       true,
+						FixedResult: reflect.ValueOf(introspection.WrapSchema(r.Schema)),
+					})
+				}
+
+			case "__type":
+				if !r.DisableIntrospection {
+					p := packer.ValuePacker{ValueType: reflect.TypeOf("")}
+					v, err := p.Pack(field.Arguments.MustGet("name").Deserialize(r.Vars))
+					if err != nil {
+						r.AddError(errors.Errorf("%s", err))
+						return nil
+					}
+
+					t, ok := r.Schema.Types[v.String()]
+					if !ok {
+						return nil
+					}
+
+					flattenedSels = append(flattenedSels, &SchemaField{
+						Field:       s.Meta.FieldType,
+						Alias:       field.Alias.Name,
+						Sels:        applySelectionSet(r, s, s.Meta.Type, field.SelectionSet),
+						Async:       true,
+						FixedResult: reflect.ValueOf(introspection.WrapType(t)),
+					})
+				}
+
+			default:
+				fe := e.Fields[field.Name.Name]
+
+				var args map[string]interface{}
+				var packedArgs reflect.Value
+				if fe.ArgsPacker != nil {
+					args = make(map[string]interface{})
+					for _, arg := range field.Arguments {
+						args[arg.Name.Name] = arg.Value.Deserialize(r.Vars)
+					}
+					var err error
+					packedArgs, err = fe.ArgsPacker.Pack(args)
+					if err != nil {
+						r.AddError(errors.Errorf("%s", err))
+						return
+					}
+				}
+
+				fieldSels := applyField(r, s, fe.ValueExec, field.SelectionSet)
+				flattenedSels = append(flattenedSels, &SchemaField{
+					Field:      *fe,
+					Alias:      field.Alias.Name,
+					Args:       args,
+					PackedArgs: packedArgs,
+					Sels:       fieldSels,
+					Async:      fe.HasContext || fe.ArgsPacker != nil || fe.HasError || HasAsyncSel(fieldSels),
+				})
+			}
+
+		case *types.InlineFragment:
+			frag := sel
+			if skipByDirective(r, frag.Directives) {
+				continue
+			}
+			flattenedSels = append(flattenedSels, applyFragment(r, s, e, &frag.Fragment)...)
+
+		case *types.FragmentSpread:
+			spread := sel
+			if skipByDirective(r, spread.Directives) {
+				continue
+			}
+			flattenedSels = append(flattenedSels, applyFragment(r, s, e, &r.Doc.Fragments.Get(spread.Name.Name).Fragment)...)
+
+		default:
+			panic("invalid type")
+		}
+	}
+	return
+}
+
+func applyFragment(r *Request, s *resolvable.Schema, e *resolvable.Object, frag *types.Fragment) []Selection {
+	if frag.On.Name != e.Name {
+		t := r.Schema.Resolve(frag.On.Name)
+		face, ok := t.(*types.InterfaceTypeDefinition)
+		if !ok && frag.On.Name != "" {
+			a, ok2 := e.TypeAssertions[frag.On.Name]
+			if !ok2 {
+				panic(fmt.Errorf("%q does not implement %q", frag.On, e.Name)) // TODO proper error handling
+			}
+
+			return []Selection{&TypeAssertion{
+				TypeAssertion: *a,
+				Sels:          applySelectionSet(r, s, a.TypeExec.(*resolvable.Object), frag.Selections),
+			}}
+		}
+		if ok && len(face.PossibleTypes) > 0 {
+			sels := []Selection{}
+			for _, t := range face.PossibleTypes {
+				if t.Name == e.Name {
+					return applySelectionSet(r, s, e, frag.Selections)
+				}
+
+				if a, ok := e.TypeAssertions[t.Name]; ok {
+					sels = append(sels, &TypeAssertion{
+						TypeAssertion: *a,
+						Sels:          applySelectionSet(r, s, a.TypeExec.(*resolvable.Object), frag.Selections),
+					})
+				}
+			}
+			if len(sels) == 0 {
+				panic(fmt.Errorf("%q does not implement %q", e.Name, frag.On)) // TODO proper error handling
+			}
+			return sels
+		}
+	}
+	return applySelectionSet(r, s, e, frag.Selections)
+}
+
+func applyField(r *Request, s *resolvable.Schema, e resolvable.Resolvable, sels []types.Selection) []Selection {
+	switch e := e.(type) {
+	case *resolvable.Object:
+		return applySelectionSet(r, s, e, sels)
+	case *resolvable.List:
+		return applyField(r, s, e.Elem, sels)
+	case *resolvable.Scalar:
+		return nil
+	default:
+		panic("unreachable")
+	}
+}
+
+func skipByDirective(r *Request, directives types.DirectiveList) bool {
+	if d := directives.Get("skip"); d != nil {
+		p := packer.ValuePacker{ValueType: reflect.TypeOf(false)}
+		v, err := p.Pack(d.Arguments.MustGet("if").Deserialize(r.Vars))
+		if err != nil {
+			r.AddError(errors.Errorf("%s", err))
+		}
+		if err == nil && v.Bool() {
+			return true
+		}
+	}
+
+	if d := directives.Get("include"); d != nil {
+		p := packer.ValuePacker{ValueType: reflect.TypeOf(false)}
+		v, err := p.Pack(d.Arguments.MustGet("if").Deserialize(r.Vars))
+		if err != nil {
+			r.AddError(errors.Errorf("%s", err))
+		}
+		if err == nil && !v.Bool() {
+			return true
+		}
+	}
+
+	return false
+}
+
+func HasAsyncSel(sels []Selection) bool {
+	for _, sel := range sels {
+		switch sel := sel.(type) {
+		case *SchemaField:
+			if sel.Async {
+				return true
+			}
+		case *TypeAssertion:
+			if HasAsyncSel(sel.Sels) {
+				return true
+			}
+		case *TypenameField:
+			// sync
+		default:
+			panic("unreachable")
+		}
+	}
+	return false
+}
diff --git a/vendor/github.com/graph-gophers/graphql-go/internal/exec/subscribe.go b/vendor/github.com/graph-gophers/graphql-go/internal/exec/subscribe.go
new file mode 100644
index 00000000..37ebacbc
--- /dev/null
+++ b/vendor/github.com/graph-gophers/graphql-go/internal/exec/subscribe.go
@@ -0,0 +1,179 @@
+package exec
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"reflect"
+	"time"
+
+	"github.com/graph-gophers/graphql-go/errors"
+	"github.com/graph-gophers/graphql-go/internal/exec/resolvable"
+	"github.com/graph-gophers/graphql-go/internal/exec/selected"
+	"github.com/graph-gophers/graphql-go/types"
+)
+
+type Response struct {
+	Data   json.RawMessage
+	Errors []*errors.QueryError
+}
+
+func (r *Request) Subscribe(ctx context.Context, s *resolvable.Schema, op *types.OperationDefinition) <-chan *Response {
+	var result reflect.Value
+	var f *fieldToExec
+	var err *errors.QueryError
+	func() {
+		defer r.handlePanic(ctx)
+
+		sels := selected.ApplyOperation(&r.Request, s, op)
+		var fields []*fieldToExec
+		collectFieldsToResolve(sels, s, s.Resolver, &fields, make(map[string]*fieldToExec))
+
+		// TODO: move this check into validation.Validate
+		if len(fields) != 1 {
+			err = errors.Errorf("%s", "can subscribe to at most one subscription at a time")
+			return
+		}
+		f = fields[0]
+
+		var in []reflect.Value
+		if f.field.HasContext {
+			in = append(in, reflect.ValueOf(ctx))
+		}
+		if f.field.ArgsPacker != nil {
+			in = append(in, f.field.PackedArgs)
+		}
+		callOut := f.resolver.Method(f.field.MethodIndex).Call(in)
+		result = callOut[0]
+
+		if f.field.HasError && !callOut[1].IsNil() {
+			switch resolverErr := callOut[1].Interface().(type) {
+			case *errors.QueryError:
+				err = resolverErr
+			case error:
+				err = errors.Errorf("%s", resolverErr)
+				err.ResolverError = resolverErr
+			default:
+				panic(fmt.Errorf("can only deal with *QueryError and error types, got %T", resolverErr))
+			}
+		}
+	}()
+
+	// Handles the case where the locally executed func above panicked
+	if len(r.Request.Errs) > 0 {
+		return sendAndReturnClosed(&Response{Errors: r.Request.Errs})
+	}
+
+	if f == nil {
+		return sendAndReturnClosed(&Response{Errors: []*errors.QueryError{err}})
+	}
+
+	if err != nil {
+		if _, nonNullChild := f.field.Type.(*types.NonNull); nonNullChild {
+			return sendAndReturnClosed(&Response{Errors: []*errors.QueryError{err}})
+		}
+		return sendAndReturnClosed(&Response{Data: []byte(fmt.Sprintf(`{"%s":null}`, f.field.Alias)), Errors: []*errors.QueryError{err}})
+	}
+
+	if ctxErr := ctx.Err(); ctxErr != nil {
+		return sendAndReturnClosed(&Response{Errors: []*errors.QueryError{errors.Errorf("%s", ctxErr)}})
+	}
+
+	c := make(chan *Response)
+	// TODO: handle resolver nil channel better?
+	if result.IsZero() {
+		close(c)
+		return c
+	}
+
+	go func() {
+		for {
+			// Check subscription context
+			chosen, resp, ok := reflect.Select([]reflect.SelectCase{
+				{
+					Dir:  reflect.SelectRecv,
+					Chan: reflect.ValueOf(ctx.Done()),
+				},
+				{
+					Dir:  reflect.SelectRecv,
+					Chan: result,
+				},
+			})
+			switch chosen {
+			// subscription context done
+			case 0:
+				close(c)
+				return
+			// upstream received
+			case 1:
+				// upstream closed
+				if !ok {
+					close(c)
+					return
+				}
+
+				subR := &Request{
+					Request: selected.Request{
+						Doc:    r.Request.Doc,
+						Vars:   r.Request.Vars,
+						Schema: r.Request.Schema,
+					},
+					Limiter: r.Limiter,
+					Tracer:  r.Tracer,
+					Logger:  r.Logger,
+				}
+				var out bytes.Buffer
+				func() {
+					timeout := r.SubscribeResolverTimeout
+					if timeout == 0 {
+						timeout = time.Second
+					}
+
+					subCtx, cancel := context.WithTimeout(ctx, timeout)
+					defer cancel()
+
+					// resolve response
+					func() {
+						defer subR.handlePanic(subCtx)
+
+						var buf bytes.Buffer
+						subR.execSelectionSet(subCtx, f.sels, f.field.Type, &pathSegment{nil, f.field.Alias}, s, resp, &buf)
+
+						propagateChildError := false
+						if _, nonNullChild := f.field.Type.(*types.NonNull); nonNullChild && resolvedToNull(&buf) {
+							propagateChildError = true
+						}
+
+						if !propagateChildError {
+							out.WriteString(fmt.Sprintf(`{"%s":`, f.field.Alias))
+							out.Write(buf.Bytes())
+							out.WriteString(`}`)
+						}
+					}()
+
+					if err := subCtx.Err(); err != nil {
+						c <- &Response{Errors: []*errors.QueryError{errors.Errorf("%s", err)}}
+						return
+					}
+
+					// Send response within timeout
+					// TODO: maybe block until sent?
+					select {
+					case <-subCtx.Done():
+					case c <- &Response{Data: out.Bytes(), Errors: subR.Errs}:
+					}
+				}()
+			}
+		}
+	}()
+
+	return c
+}
+
+func sendAndReturnClosed(resp *Response) chan *Response {
+	c := make(chan *Response, 1)
+	c <- resp
+	close(c)
+	return c
+}