code: func (s *Server) Start() error {
  	if len(s.getCommandLabels()) > 0 {
  		s.updateLabels()
  	}
  	go s.heartbeat.Run()
  
  	// If the server requested connections to it arrive over a reverse tunnel,
  	// don't call Start() which listens on a socket, return right away.
  	if s.useTunnel {
  		return nil
  	}
  	return s.srv.Start()
  }
docs: // Start starts server