code: func (s *StanServer) sendMsgToQueueGroup(qs *queueState, m *pb.MsgProto, force bool) (*subState, bool, bool) {
  	sub := findBestQueueSub(qs.subs)
  	if sub == nil {
  		return nil, false, false
  	}
  	sub.Lock()
  	wasStalled := sub.stalled
  	didSend, sendMore := s.sendMsgToSub(sub, m, force)
  	// If this is not a redelivery and the sub was not stalled, but now is,
  	// bump the number of stalled members.
  	if !force && !wasStalled && sub.stalled {
  		qs.stalledSubCount++
  	}
  	if didSend && sub.LastSent > qs.lastSent {
  		qs.lastSent = sub.LastSent
  	}
  	sub.Unlock()
  	return sub, didSend, sendMore
  }
docs: // Send a message to the queue group
  // Assumes qs lock held for write