The net/http Package in Go

The net/http package in Go is a powerful tool for building HTTP servers and clients. It provides a rich set of functionalities for handling HTTP requests and responses, making it a versatile package for a wide range of web-related tasks.

Setting Up a Simple HTTP Server

Let's delve into a simple example of how to set up an HTTP server using the net/http package.

package main

import (
    "fmt"
    "net/http"
)

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

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

This program sets up a server that listens on port 8080 and responds with "Hello, World!" for any request to the root ("/") path.

Handling HTTP Requests

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

The http.HandleFunc function is used to define how the server responds to specific routes. The provided function takes two parameters: http.ResponseWriter and *http.Request. The response writer is used to send the response back to the client, and the request contains information about the incoming request.

Starting the Server

http.ListenAndServe(":8080", nil)

This line starts the HTTP server. It listens on port 8080, and the nil argument means that it will use the default ServeMux (multiplexer) provided by the http package. The server will handle incoming HTTP requests based on the registered handlers.

Working with Query Parameters

You can easily handle query parameters using the r.URL.Query() method. Let's modify our server to greet a user based on a provided name parameter:

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        name := r.URL.Query().Get("name")
        if name == "" {
            name = "Guest"
        }
        fmt.Fprintf(w, "Hello, %s!", name)
    })

    // ... rest of the code
}

Now, you can visit http://localhost:8080/?name=John and the server will respond with "Hello, John!"

Serving Static Files

staticDir := http.Dir("./static")
fileServer := http.FileServer(staticDir)
http.Handle("/static/", http.StripPrefix("/static/", fileServer))

Create a 'static' folder alongside your main.go file and add any static files like HTML, CSS, and JavaScript. For example, you created hello.html inside the 'static' folder.

Now, when you visit http://localhost:8080/static/hello.html, you will be able to see your HTML served.

Explanation:

The http.Dir function is used to convert a string (representing a directory path) into a type that implements the http.FileSystem interface.

The http.FileServer function is used to serve static files in the directory.

The http.StripPrefix function is used to remove the "/static/" prefix from the request URL before passing it to the file server. This is useful to avoid exposing the actual directory structure in the URL.