Building a Web Server in Go: A Beginner's Guide

Creating a web server might sound complex, but it's simple with the Go standard library. In this article, we’ll walk through building a minimal web server from scratch. This server will:

1. Respond to requests at the root URL ( / ) by displaying details about the request.

2. Provide a /count endpoint to track the total number of requests made.

The Code

Here’s the complete Go program for our web server

package main

import (
    "fmt"
    "log"
    "net/http"
    "sync"
)

var mu sync.Mutex
var count int

func main() {
    http.HandleFunc("/", handler)
    http.HandleFunc("/count", counter)
    log.Fatal(http.ListenAndServe("localhost:8000", nil))
}

// handler responds with details of the HTTP request
func handler(w http.ResponseWriter, r *http.Request) {
    mu.Lock()
    count++
    mu.Unlock()

    // Write details about the request
    fmt.Fprintf(w, "%s %s %s\n", r.Method, r.URL, r.Proto)
    for k, v := range r.Header {
        fmt.Fprintf(w, "Header[%q] = %q\n", k, v)
    }
    fmt.Fprintf(w, "Host = %q\n", r.Host)
    fmt.Fprintf(w, "RemoteAddr = %q\n", r.RemoteAddr)

    // Parse and display form data if any
    if err := r.ParseForm(); err != nil {
        log.Print(err)
    }
    for k, v := range r.Form {
        fmt.Fprintf(w, "Form[%q] = %q\n", k, v)
    }
}

// counter responds with the total number of requests
func counter(w http.ResponseWriter, r *http.Request) {
    mu.Lock()
    fmt.Fprintf(w, "Count %d\n", count)
    mu.Unlock()
}

Some parts of the code

How It Works

1. Handler Functions:

   • Handler: This function is tied to the root URL( / ). It processes incoming requests, increments the request count, and returns detailed information about the request.

   • Counter: This function is tied to the /count URL. It responds with the total number of requests the server has received.

2. Concurrency Management:

   The sync.Mutex ensures safe updates to the count variable when multiple requests are being processed at the same time.

3. Starting the Server:

   The http.ListenAndServe function sets up the server to listen on localhost:8000. Every request triggers the appropriate handler function.

Running the Server

1. Save the code to a file: main.go

2. Start the server with:

    go run main.go
   

Your server is now live and listening on http://localhost:8000.

Testing the Server

Example 1: Request to /.

curl http://localhost:8000/

Response:

GET / HTTP/1.1
Header["User-Agent"] = ["curl/7.79.1"]
Header["Accept"] = ["*/*"]
Host = "localhost:8000"
RemoteAddr = "127.0.0.1:56789"

Example 2: Request to /count

Request to the /count Endpoint:

curl http://localhost:8000/count

Response:

Count 1

Each additional request to the server will increment the count.

Why Go?

Golang is a popular programming language designed by Google. Go provides many built-in libraries, such as net/http we used in this web server, and also offers efficient frameworks Gin for faster development. Additionally, Go has a clean simple syntax and is a powerful tool for handling concurrency.

What’s Next?

Now that you have built a basic web server, here are some ideas to expand it:

• Serve HTML or JSON responses.

• Add custom error handling.

• Create APIs for more advanced applications.

With Go, you can quickly move from a simple web server to a robust, production-ready application. Give it a try and see how easy it is to get started!