code: func (do *Domain) ShowSlowQuery(showSlow *ast.ShowSlow) []*SlowQueryInfo {
  	msg := &showSlowMessage{
  		request: showSlow,
  	}
  	msg.Add(1)
  	do.slowQuery.msgCh <- msg
  	msg.Wait()
  	return msg.result
  }
docs: // ShowSlowQuery returns the slow queries.