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Building a Backend Application with Go

Modify the Resolver

Explore how to implement resolvers in Go to handle GraphQL operations such as user registration, login, and blog management. Understand how to integrate authentication middleware and configure the server to support these functionalities, enabling you to develop a complete GraphQL backend application.

We'll cover the following...

Implement the resolver

Inside the schema.resolvers.go file, we implement all the resolvers.

Register

First, we implement the resolver for the registration.

Go (1.18.2)
func (r *mutationResolver) Register(ctx context.Context, input model.NewUser) (string, error) {
    // perform an user registration
    var token string = r.userService.Register(input)
    // if JWT token is empty, return an error
    if token == "" {
        return "", errors.New("registration failed")
    }
    // return JWT token
    return token, nil
}

Below is an explanation of the code above:

  • In line 3, the r.userService.Register(input) function performs user registration. This function returns the JWT token.

  • In line 11, if the registration succeeds, the JWT token is returned.

Login

We implement the resolver for the login.

Go (1.18.2)
func (r *mutationResolver) Login(ctx context.Context, input model.LoginInput) (string, error) {

    // perform a login

    var token string = r.userService.Login(input)



    // if JWT token is empty, return an error

    if token == "" {

        return "", errors.New("login failed, invalid email or password")

    }



    // return JWT token

    return token, nil

}

Below is an explanation of the code above:

  • In line 3, the r.userService.Login(input) function performs a login for the registered user.

  • In line 11, if the login is successful, the JWT token is returned.

Create a new blog

We implement the resolver for creating a new blog.

Go (1.18.2)
func (r *mutationResolver) NewBlog(ctx context.Context, input model.NewBlog) (*model.Blog, error) {

    // get the user from the middleware

    user := middleware.ForContext(ctx)

    // if the user does not exist, return an error

    if user == nil {

        return &model.Blog{}, errors.New("access denied")

    }



    // create a new blog

    blog, err := r.blogService.CreateBlog(input, *user)



    // if blog creation failed, return an error

    if err != nil {

        return nil, err

    }



    // return the recently created blog

    return blog, nil

}

Below is an explanation of the code above: ...