Add middleware in Go web servers

Add middleware to a Go web server by wrapping your handler with a function that executes before or after the request reaches your main logic.

func loggingMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        log.Println(r.Method, r.URL.Path)
        next.ServeHTTP(w, r)
    })
}

func main() {
    mux := http.NewServeMux()
    mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        w.Write([]byte("Hello, World"))
    })
    http.ListenAndServe(":8080", loggingMiddleware(mux))
}

Middleware is code that runs before or after your main request handler to perform tasks like logging, authentication, or compression. Think of it as a security guard checking IDs before letting visitors into a building. You wrap your server logic with these functions to add features without changing your core code.