code: func (r *Router) checkMethod(node *Trie, method string) http.Handler {
  	for _, h := range node.Handler {
  		if h.Method == "ALL" {
  			return h.Handler
  		}
  		if h.Method == method {
  			return h.Handler
  		}
  	}
  	if r.NotAllowedHandler != nil {
  		return r.NotAllowedHandler
  	}
  	return r.MethodNotAllowed()
  }
docs: // checkMethod check if request method is allowed or not