code: func (cc *LBClient) Do(req *Request, resp *Response) error {
  	timeout := cc.Timeout
  	if timeout <= 0 {
  		timeout = DefaultLBClientTimeout
  	}
  	return cc.DoTimeout(req, resp, timeout)
  }
docs: // Do calls calculates deadline using LBClient.Timeout and calls DoDeadline
  // on the least loaded client.