Path variable not parsed about mux HOT 2 OPEN

package main

import (
	"fmt"
	"log"
	"net/http"
	"time"

	"github.com/gorilla/handlers"
	"github.com/gorilla/mux"
)

func YourHandler(w http.ResponseWriter, r *http.Request) {
	w.Write([]byte("Ping!\n"))
}

func FindUserById(w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	id, ok := vars["id"]
	if !ok {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte("userId is required"))
		return
	}
	fmt.Println("User id " + id)
	
	w.WriteHeader(http.StatusOK)
	w.Write([]byte("User id" + id))
}

func main() {
	r := mux.NewRouter()
	// Routes consist of a path and a handler function.
	r.HandleFunc("/ping", YourHandler)
	r.HandleFunc("/user/{id}", FindUserById)
	// Bind to a port and pass our router in

	ch := handlers.CORS(handlers.AllowedOrigins([]string{"*"}))
	//log.Fatal(http.ListenAndServe(":8000", ch(r)))
	s := http.Server{
		Addr:         "localhost:8000",
		Handler:      ch(r),
		ReadTimeout:  5 * time.Second,
		WriteTimeout: 10 * time.Second,
		IdleTimeout:  120 * time.Second,
	}

	log.Fatal(s.ListenAndServe())
}

package main

import (
	"log"
	"net/http"
	"time"

	"github.com/gorilla/mux"
)

func main() {
	r := mux.NewRouter()
	r.HandleFunc("/", HomeHandler)
	r.HandleFunc("/v1/user/{id}", FindUserById())

	s := http.Server{
		Addr:         "localhost:8000",
		Handler:      r,
		ReadTimeout:  5 * time.Second,
		WriteTimeout: 10 * time.Second,
		IdleTimeout:  120 * time.Second,
	}

	log.Fatal(s.ListenAndServe())
}

func HomeHandler(w http.ResponseWriter, r *http.Request) {
	_, _ = w.Write([]byte("Hello"))
}

func FindUserById() http.HandlerFunc {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		vars := mux.Vars(r)
		id, ok := vars["id"]
		if !ok {
			w.WriteHeader(http.StatusBadRequest)
			_, _ = w.Write([]byte("userId is required"))
			return
		}
		w.WriteHeader(http.StatusOK)
		_, _ = w.Write([]byte(id))
	})
}