How to Implement Request ID Middleware in Go

Implement Request ID middleware by generating a unique ID for each request and storing it in the context before passing it to the next handler.

func RequestIDMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        id := uuid.New().String()
        ctx := context.WithValue(r.Context(), "requestID", id)
        w.Header().Set("X-Request-ID", id)
        next.ServeHTTP(w, r.WithContext(ctx))
    })
}

Use this middleware in your server setup:

mux := http.NewServeMux()
mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
    id := r.Context().Value("requestID").(string)
    fmt.Fprintf(w, "Request ID: %s", id)
})

http.ListenAndServe(":8080", RequestIDMiddleware(mux))

Request ID middleware in Go adds a unique tracking number to every request your server receives. It lets you trace a specific user's journey through your logs and services by looking up that number. Think of it like a receipt number that follows a customer through every step of a transaction.