code: func (s *Server) KillAllConnections() {
  	s.rwlock.Lock()
  	defer s.rwlock.Unlock()
  	logutil.Logger(context.Background()).Info("[server] kill all connections.")
  
  	for _, conn := range s.clients {
  		atomic.StoreInt32(&conn.status, connStatusShutdown)
  		terror.Log(errors.Trace(conn.closeWithoutLock()))
  		killConn(conn)
  	}
  }
docs: // KillAllConnections kills all connections when server is not gracefully shutdown.