update resolver definition to use channels for subscriptions

codegen/build.go

@@ -10,14 +10,15 @@ import (
 )
 
 type Build struct {
-	PackageName  string
-	Objects      Objects
-	Inputs       Objects
-	Interfaces   []*Interface
-	Imports      Imports
-	QueryRoot    *Object
-	MutationRoot *Object
-	SchemaRaw    string
+	PackageName      string
+	Objects          Objects
+	Inputs           Objects
+	Interfaces       []*Interface
+	Imports          Imports
+	QueryRoot        *Object
+	MutationRoot     *Object
+	SubscriptionRoot *Object
+	SchemaRaw        string
 }
 
 // Bind a schema together with some code to generate a Build
@@ -48,6 +49,10 @@ func Bind(schema *schema.Schema, userTypes map[string]string, destDir string) (*
 		b.MutationRoot = b.Objects.ByName(mr.TypeName())
 	}
 
+	if sr, ok := schema.EntryPoints["subscription"]; ok {
+		b.SubscriptionRoot = b.Objects.ByName(sr.TypeName())
+	}
+
 	// Poke a few magic methods into query
 	q := b.Objects.ByName(b.QueryRoot.GQLType)
 	q.Fields = append(q.Fields, Field{

codegen/object.go

@@ -16,6 +16,7 @@ type Object struct {
 	Satisfies          []string
 	Root               bool
 	DisableConcurrency bool
+	Stream             bool
 }
 
 type Field struct {
@@ -75,7 +76,12 @@ func (f *Field) ResolverDeclaration() string {
 		res += fmt.Sprintf(", %s %s", arg.GQLName, arg.Signature())
 	}
 
-	res += fmt.Sprintf(") (%s, error)", f.Signature())
+	result := f.Signature()
+	if f.Object.Stream {
+		result = "chan<-" + result
+	}
+
+	res += fmt.Sprintf(") (%s, error)", result)
 	return res
 }
 

codegen/object_build.go

@@ -36,6 +36,9 @@ func buildObjects(types NamedTypes, s *schema.Schema, prog *loader.Program) Obje
 		if name == "mutation" {
 			objects.ByName(obj.Name).DisableConcurrency = true
 		}
+		if name == "subscription" {
+			objects.ByName(obj.Name).Stream = true
+		}
 	}
 
 	sort.Slice(objects, func(i, j int) bool {

templates/file.go

@@ -50,6 +50,9 @@ func NewExecutor(resolvers Resolvers) func(context.Context, string, string, map[
 		{{- if .MutationRoot}}
 		} else if op.Type == query.Mutation {
 			data = c._{{.MutationRoot.GQLType|lcFirst}}(op.Selections, nil)
+		{{- end}}{{ if .SubscriptionRoot}}
+		} else if op.Type == query.Subscription {
+			data = c._{{.SubscriptionRoot.GQLType|lcFirst}}(op.Selections, nil)
 		{{- end}}
 		} else {
 			return []*errors.QueryError{errors.Errorf("unsupported operation type")}