code: func (mx *Mux) Route(pattern string, fn func(r Router)) Router {
  	subRouter := NewRouter()
  	if fn != nil {
  		fn(subRouter)
  	}
  	mx.Mount(pattern, subRouter)
  	return subRouter
  }
docs: // Route creates a new Mux with a fresh middleware stack and mounts it
  // along the `pattern` as a subrouter. Effectively, this is a short-hand
  // call to Mount. See _examples/.