Creating REST APIs with Go: Step-by-Step

In this article, we’ll guide you through creating a simple REST API using the Go programming language. REST APIs are essential components for many software applications, enabling different software systems to communicate with each other over the internet. Let’s dive into building a REST API in Go step-by-step.

Prerequisites

Before starting, make sure you have Go installed on your machine. You can download and install it from the official Go website. Additionally, you will need a code editor like Visual Studio Code, and a command line terminal to execute Go commands.

Step 1: Create a New Go Project

First, let's create a new directory for our project and initialize it as a Go module:

$ mkdir restapi

$ cd restapi

$ go mod init example.com/restapi

Step 2: Set Up the HTTP Server

Go has excellent built-in support for HTTP. Add the following code to create a simple HTTP server:

package main

import (
    "fmt"
    "net/http"
)

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        fmt.Fprintf(w, "Hello, World!")
    })

    http.ListenAndServe(":8080", nil)
}

This code sets up an HTTP server on port 8080 that returns "Hello, World!" when accessed at the root URL.

Step 3: Define API Endpoints

Now, it’s time to define some API endpoints. For this example, we will create endpoints to fetch and create items. Update your main file as follows:

package main

import (
    "encoding/json"
    "net/http"
)

type Item struct {
    ID   string `json:"id"`
    Name string `json:"name"`
}

var inventory = []Item{
    {ID: "1", Name: "Item1"},
    {ID: "2", Name: "Item2"},
}

func main() {
    http.HandleFunc("/items", getItems)
    http.HandleFunc("/items/add", addItem)

    http.ListenAndServe(":8080", nil)
}

func getItems(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(inventory)
}

func addItem(w http.ResponseWriter, r *http.Request) {
    var newItem Item
    json.NewDecoder(r.Body).Decode(&newItem)
    inventory = append(inventory, newItem)

    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(newItem)
}