Getting Started Using dep

Building GraphQL servers in golang


This tutorial uses the dep tool to manage dependencies instead of Go Modules and should be considered a deprecated way to use gqlgen. Read out new Getting Started guide for instructions for using Go Modules.

This tutorial will take you through the process of building a GraphQL server with gqlgen that can:

You can find the finished code for this tutorial here

Install gqlgen

This article uses dep to install gqlgen. Follow the instructions for your environment to install.

Assuming you already have a working Go environment, create a directory for the project in your $GOPATH:

$ mkdir -p $GOPATH/src/[username]/gqlgen-todos

Add the following file to your project under scripts/gqlgen.go:

// +build ignore

package main

import ""

func main() {

Lastly, initialise dep. This will inspect any imports you have in your project, and pull down the latest tagged release.

$ dep init

Building the server

Define the schema

gqlgen is a schema-first library — before writing code, you describe your API using the GraphQL Schema Definition Language. This usually goes into a file called schema.graphql:

type Todo {
  id: ID!
  text: String!
  done: Boolean!
  user: User!

type User {
  id: ID!
  name: String!

type Query {
  todos: [Todo!]!

input NewTodo {
  text: String!
  userId: String!

type Mutation {
  createTodo(input: NewTodo!): Todo!

Create the project skeleton

$ go run scripts/gqlgen.go init

This has created an empty skeleton with all files you need:

Now run dep ensure, so that we can ensure that the newly generated code’s dependencies are all present:

 $ dep ensure

Create the database models

The generated model for Todo isn’t right, it has a user embeded in it but we only want to fetch it if the user actually requested it. So instead lets make a new model in todo.go:

package gettingstarted

type Todo struct {
	ID     string
	Text   string
	Done   bool
	UserID string

Next tell gqlgen to use this new struct by adding it to gqlgen.yml:


Regenerate by running:

$ go run scripts/gqlgen.go -v
Unable to bind Todo.user to[username]/gqlgen-todos/gettingstarted.Todo
	no method named user
	no field named user
	Adding resolver method


The verbose flag -v is here to show what gqlgen is doing. It has looked at all the fields on the model and found matching methods for all of them, except user. For user it has added a resolver to the interface you need to implement. This is the magic that makes gqlgen work so well!

Implement the resolvers

The generated runtime has defined an interface for all the missing resolvers that we need to provide. Lets take a look in generated.go

// NewExecutableSchema creates an ExecutableSchema from the ResolverRoot interface.
func NewExecutableSchema(cfg Config) graphql.ExecutableSchema {
	return &executableSchema{
		resolvers:  cfg.Resolvers,
		directives: cfg.Directives,

type Config struct {
	Resolvers  ResolverRoot
	Directives DirectiveRoot

type ResolverRoot interface {
	Mutation() MutationResolver
	Query() QueryResolver
	Todo() TodoResolver

type DirectiveRoot struct {
type MutationResolver interface {
	CreateTodo(ctx context.Context, input NewTodo) (Todo, error)
type QueryResolver interface {
	Todos(ctx context.Context) ([]Todo, error)
type TodoResolver interface {
	User(ctx context.Context, obj *Todo) (User, error)

Notice the TodoResolver.User method? Thats gqlgen saying “I dont know how to get a User from a Todo, you tell me.”. Its worked out how to build everything else for us.

For any missing models (like NewTodo) gqlgen will generate a go struct. This is usually only used for input types and one-off return values. Most of the time your types will be coming from the database, or an API client so binding is better than generating.

Write the resolvers

This is a work in progress, we have a way to generate resolver stubs, but it cannot currently update existing code. We can force it to run again by deleting resolver.go and re-running gqlgen:

$ rm resolver.go
$ go run scripts/gqlgen.go

Now we just need to fill in the not implemented parts. Update resolver.go

package gettingstarted

import (
	context "context"

type Resolver struct {
	todos []Todo

func (r *Resolver) Mutation() MutationResolver {
	return &mutationResolver{r}
func (r *Resolver) Query() QueryResolver {
	return &queryResolver{r}
func (r *Resolver) Todo() TodoResolver {
	return &todoResolver{r}

type mutationResolver struct{ *Resolver }

func (r *mutationResolver) CreateTodo(ctx context.Context, input NewTodo) (*Todo, error) {
	todo := &Todo{
		Text:   input.Text,
		ID:     fmt.Sprintf("T%d", rand.Int()),
		UserID: input.UserID,
	r.todos = append(r.todos, *todo)
	return todo, nil

type queryResolver struct{ *Resolver }

func (r *queryResolver) Todos(ctx context.Context) ([]Todo, error) {
	return r.todos, nil

type todoResolver struct{ *Resolver }

func (r *todoResolver) User(ctx context.Context, obj *Todo) (*User, error) {
	return &User{ID: obj.UserID, Name: "user " + obj.UserID}, nil

We now have a working server, to start it:

go run server/server.go

then open http://localhost:8080 in a browser. here are some queries to try:

mutation createTodo {
  createTodo(input:{text:"todo", userId:"1"}) {
    user {

query findTodos {
  	todos {
      user {

Finishing touches

At the top of our resolver.go add the following line:

//go:generate go run scripts/gqlgen.go -v

This magic comment tells go generate what command to run when we want to regenerate our code. To run go generate recursively over your entire project, use this command:

go generate ./...


Ensure that the path to your gqlgen binary is relative to the file the generate command is added to.