Setting Up a GraphQL API with Golang and GQLGen

GraphQL is a powerful query language for APIs, and GQLGen makes it easy to build a GraphQL server in Go. In this tutorial, we’ll go through the steps to set up a simple GraphQL API using Golang and GQLGen.

Prerequisites

Before we start, make sure you have the following installed:

• Go
• Git

Step 1: Create a New Go Module

Start by creating a new Go module:

mkdir gqlgen-example
cd gqlgen-example
go mod init gqlgen-example

Step 2: Install GQLGen

Install the GQLGen tool and dependencies:

go install github.com/99designs/gqlgen@latest
go get github.com/99designs/gqlgen/graphql-go

Run the gqlgen command to initialize your project:

gqlgen init

This command generates a basic GraphQL setup, including a schema.graphqls file and boilerplate code.

Step 3: Define Your Schema

Edit the schema.graphqls file to define your GraphQL schema. For example:

type Query {
  hello: String!
}

Step 4: Implement Resolvers

GQLGen generates resolver interfaces based on your schema. Implement the Query resolver in resolver.go:

package gqlgen_example

func (r *queryResolver) Hello() (string, error) {
    return "Hello, world!", nil
}

Step 5: Run the Server

Start your GraphQL server by running:

go run server.go

You can now access the GraphQL playground at http://localhost:8080/ to test your API.

Step 6: Test Your API

In the GraphQL playground, run the following query:

query {
  hello
}

You should see the response:

{
  "data": {
    "hello": "Hello, world!"
  }
}

Conclusion

That’s it! You’ve successfully set up a basic GraphQL API using Golang and GQLGen. From here, you can expand your schema and resolvers to build a more complex API.