code: func (r *Router) MethodNotAllowed() http.HandlerFunc {
  	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
  		http.Error(w,
  			http.StatusText(http.StatusMethodNotAllowed),
  			http.StatusMethodNotAllowed,
  		)
  	})
  }
docs: // MethodNotAllowed default handler for 405