How to Implement JWT Authentication in Chi API

# Implementing JWT Authentication in a Chi API: A Practical Guide

![An abstract geometric pattern of interlocking golden keys floating in space with soft light rays streaming through crystalline structures in bright yellow and silver tones viewed from a dramatic low angle perspective high-quality ultra-realistic cinematic 8K UHD high resolution sharp and detail](/image_generation/tillitsdone_Golang_Chi_topics_find_How-to-Implement-JWT-Authentication-in-a-Chi-APIcontent_1732686623921_0.jpeg "An abstract geometric pattern of interlocking golden keys floating in space with soft light rays streaming through crystalline structures in bright yellow and silver tones viewed from a dramatic low angle perspective high-quality ultra-realistic cinematic 8K UHD high resolution sharp and detail")

Securing your Go web applications is crucial in today's digital landscape. In this guide, we'll walk through implementing JWT (JSON Web Token) authentication in a Chi router-based API. We'll create a robust authentication system that's both secure and scalable.

## Setting Up the Project

First, let's set up our project structure and install the necessary dependencies. We'll need the Chi router and a JWT package:

```go
go get -u github.com/go-chi/chi/v5
go get -u github.com/golang-jwt/jwt/v5

func JWTMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        tokenString := r.Header.Get("Authorization")
        if tokenString == "" {
            http.Error(w, "Unauthorized", http.StatusUnauthorized)
            return
        }

        token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
            return []byte(os.Getenv("JWT_SECRET")), nil
        })

        if err != nil || !token.Valid {
            http.Error(w, "Unauthorized", http.StatusUnauthorized)
            return
        }

        next.ServeHTTP(w, r)
    })
}

func Login(w http.ResponseWriter, r *http.Request) {
    // Validate user credentials here

    claims := jwt.MapClaims{
        "user_id": user.ID,
        "exp":     time.Now().Add(time.Hour * 24).Unix(),
    }

    token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
    tokenString, err := token.SignedString([]byte(os.Getenv("JWT_SECRET")))

    if err != nil {
        http.Error(w, "Error generating token", http.StatusInternalServerError)
        return
    }

    json.NewEncoder(w).Encode(map[string]string{
        "token": tokenString,
    })
}

func main() {
    r := chi.NewRouter()

    // Public routes
    r.Post("/login", Login)

    // Protected routes
    r.Group(func(r chi.Router) {
        r.Use(JWTMiddleware)
        r.Get("/protected", ProtectedHandler)
    })
}