func main() { schema, err := tools.MakeExecutableSchema(tools.ExecutableSchema{ TypeDefs: `  directive @description(value: String!) on FIELD_DEFINITION   type Foo {  id: ID!  name: String!  description: String  }    type Query {  foo(id: ID!): Foo @description(value: "bazqux")  }`, Resolvers: tools.ResolverMap{ "Query": &tools.ObjectResolver{ Fields: tools.FieldResolveMap{ "foo": &tools.FieldResolver{ Resolve: func(p graphql.ResolveParams) (interface{}, error) { // lookup data return foo, nil } }, }, }, }, SchemaDirectives: tools.SchemaDirectiveVisitorMap{ "description": &tools.SchemaDirectiveVisitor{ VisitFieldDefinition: func(field *graphql.Field, args map[string]interface{}) { resolveFunc := field.Resolve field.Resolve = func(p graphql.ResolveParams) (interface{}, error) { result, err := resolveFunc(p) if err != nil { return result, err } data := result.(map[string]interface{}) data["description"] = args["value"] return data, nil } }, }, }, }) if err != nil { log.Fatalf("Failed to build schema, error: %v", err) } params := graphql.Params{ Schema: schema, RequestString: `  query GetFoo {  foo(id: "5cffbf1ccecefcfff659cea8") {  description  }  }`, } r := graphql.Do(params) if r.HasErrors() { log.Fatalf("failed to execute graphql operation, errors: %+v", r.Errors)	} rJSON, _ := json.Marshal(r) fmt.Printf("%s \n", rJSON) }