code: func (s *Health) OpenMonitorChannel() chan struct{} {
  	s.mu.Lock()
  	defer s.mu.Unlock()
  
  	if s.stop == nil {
  		logrus.Debug("OpenMonitorChannel")
  		s.stop = make(chan struct{})
  		return s.stop
  	}
  	return nil
  }
docs: // OpenMonitorChannel creates and returns a new monitor channel. If there
  // already is one, it returns nil.