code: func NewResponseTimeReporter(handler httpx.Handler, router *httpx.Router) *responseTimeReporter {
  	if router == nil {
  		panic("NewResponseTimeReporter: router is requred")
  	}
  	return &responseTimeReporter{handler, router}
  }
docs: // ResponseTimeReporter reports timing metrics using metrics package
  //
  // Usage:
  //   r := httpx.NewRouter()
  //   ...
  //   r.HandleFunc("/", func(ctx context.Context, w http.ResponseWriter, r *http.Request) error {
  //   	w.WriteHeader(http.StatusCreated)
  //   	return nil
  //   }).Methods("GET")
  //   s := NewResponseTimeReporter(r, r)
  //