example.go

func (p *XImpl) Listen(_ *empty.Empty, rec services.X_ListenServer) error {
	c := make(chan *services.X, 16)
	p.add(c)
	defer p.remove(c)
	ctx := rec.Context()
	for {
		select {
		case v := <-c:
			if err := rec.Send(v); err != nil {
        return err
			}
		case <-ctx.Done():
			 return nil
		}
	}
}