Introduction
A Basic Authentication System is a fundamental security mechanism used for verifying the identity of a user. It is often employed in web applications to ensure that only authorized individuals can access certain features. In this tutorial, we will build a simple authentication system using the Go programming language. We will cover both user registration and login functionality, storing user credentials in memory (simulating a database).
Objective
The goal of this project is to create a simple authentication system that allows users to register by providing a username and password, and log in using their credentials. This will help demonstrate how to implement basic security features and manage user authentication in a Go application.
Go Program Code
package main
import (
"fmt"
"log"
"net/http"
"strings"
)
var users = make(map[string]string)
func register(w http.ResponseWriter, r *http.Request) {
if r.Method == http.MethodPost {
username := r.FormValue("username")
password := r.FormValue("password")
if username == "" || password == "" {
http.Error(w, "Username and Password cannot be empty", http.StatusBadRequest)
return
}
users[username] = password
fmt.Fprintf(w, "Registration successful! You can now log in.")
} else {
http.ServeFile(w, r, "register.html")
}
}
func login(w http.ResponseWriter, r *http.Request) {
if r.Method == http.MethodPost {
username := r.FormValue("username")
password := r.FormValue("password")
storedPassword, exists := users[username]
if !exists || storedPassword != password {
http.Error(w, "Invalid username or password", http.StatusUnauthorized)
return
}
fmt.Fprintf(w, "Login successful! Welcome, %s.", username)
} else {
http.ServeFile(w, r, "login.html")
}
}
func main() {
http.HandleFunc("/register", register)
http.HandleFunc("/login", login)
fmt.Println("Server is running on http://localhost:8080")
log.Fatal(http.ListenAndServe(":8080", nil))
}
Explanation of the Program
This program defines a simple HTTP server using the Go standard library. It handles two main routes:
- /register: Allows users to register by providing a username and password. The credentials are stored in the
usersmap, simulating a database. - /login: Allows users to log in using the username and password they registered with. If the login is successful, a welcome message is shown. If not, an error message is returned.
The program uses the http package to handle HTTP requests and responses. The register.html and login.html files should contain simple HTML forms to collect the user input. Here is a sample HTML form for registration:
<!-- register.html -->
<html>
<body>
<h2>Register</h2>
<form action="/register" method="post">
<label>Username: </label><input type="text" name="username"><br>
<label>Password: </label><input type="password" name="password"><br>
<input type="submit" value="Register">
</form>
</body>
</html>
Similarly, you can create a simple login.html form for user login.
How to Run the Program
- Ensure you have Go installed on your machine. If not, download and install it from here.
- Create a new directory for your project and create a Go file, e.g.,
main.go. - Copy and paste the Go code provided above into
main.go. - Create the
register.htmlandlogin.htmlfiles in the same directory. - Open a terminal or command prompt, navigate to the project directory, and run the command:
go run main.go. - Open a web browser and go to http://localhost:8080/register to start the registration process.
- After registration, you can log in at http://localhost:8080/login.
