code: func (g *Group) StartWithChannel(stopCh <-chan struct{}, f func(stopCh <-chan struct{})) {
  	g.Start(func() {
  		f(stopCh)
  	})
  }
docs: // StartWithChannel starts f in a new goroutine in the group.
  // stopCh is passed to f as an argument. f should stop when stopCh is available.