code: func (s *Server) TryGracefulDown() {
  	ctx, cancel := context.WithTimeout(context.Background(), gracefulCloseConnectionsTimeout)
  	defer cancel()
  	done := make(chan struct{})
  	go func() {
  		s.GracefulDown(ctx, done)
  	}()
  	select {
  	case <-ctx.Done():
  		s.KillAllConnections()
  	case <-done:
  		return
  	}
  }
docs: // TryGracefulDown will try to gracefully close all connection first with timeout. if timeout, will close all connection directly.