code: func (r *Router) Use(mwf ...MiddlewareFunc) {
  	for _, fn := range mwf {
  		r.middlewares = append(r.middlewares, fn)
  	}
  }
docs: // Use appends a MiddlewareFunc to the chain. Middleware can be used to intercept or otherwise modify requests and/or responses, and are executed in the order that they are applied to the Router.