n  int
}

func (h *countHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	h.mu.Lock()
	defer h.mu.Unlock()
	h.n++
	fmt.Fprintf(w, "count is %d\n", h.n)
}

func ExampleHandle() {
	http.Handle("/count", new(countHandler))
	log.Fatal(http.ListenAndServe(":8080", nil))