When I send 'GET' request, returning '404 page not found' in Golang

I'm new on Golang. I try to write an API server with Golang without any HTTP framework(echo, gin, etc.). I wrote 'post' endpoint but my 'get' endpoint not respond. I tried to write another get endpoint named 'ping' and it was working. My curl

curl --location 'http://localhost:8080/users/45254424-5be1-487d-9131-bad3b2f7791c'

My handler

func (u UserHandler) GetById(writer http.ResponseWriter, request *http.Request) {
	id := strings.TrimPrefix(request.URL.Path, "/users/")
	user := u.userService.GetById(uuid.Must(uuid.Parse(id)))
	writer.Header().Set("Content-Type", "application/json")
	json.NewEncoder(writer).Encode(user)
}

My main method

postgresConnection := db.NewDb()
userRepository := repository.NewUserRepository(postgresConnection)
userService := service.NewUserService(userRepository)
userHandler := handlers.NewUserHandler(userService)

mux := http.NewServeMux()
mux.HandleFunc("/users", func(writer http.ResponseWriter, request *http.Request) {
	if request.Method == "POST" {
		userHandler.Create(writer, request)
	} else {
		http.Error(writer, "Invalid request method", http.StatusMethodNotAllowed)
	}
})
mux.HandleFunc("/users/:id", func(writer http.ResponseWriter, request *http.Request) {
	if request.Method == "GET" {
		userHandler.GetById(writer, request)
	} else {
		http.Error(writer, "Invalid request method", http.StatusMethodNotAllowed)
	}
})
mux.HandleFunc("/ping", PingHandler)

err := http.ListenAndServe(":8080", mux)
log.Fatal(err)

• When registering the handler, change the patterns argument /users/:id to /users/.

mux.HandleFunc("/users/", func(writer http.ResponseWriter, request *http.Request) {
     id := strings.TrimPrefix(request.URL.Path, "/users/")

     ...
})

> Note: There are numerous third-party libraries available to assist you in writing a more readable and efficient HTTP server.
>
> Examples
>
> - Gin
> - Fiber