asyncSendMetricLoop

func (ms *metricSender) asyncSendMetricLoop() {
	for i := 0; i < ms.goNum; i++ {  // goNum变量应该是1
		go ms.sendMetricFromChan(ms.metricInfoChans[i])
	}
}

func (ms *metricSender) sendMetricFromChan(metricInfoChan chan *metricCell) {
	defer func() {
		ms.closeWG.Done()
		if r := recover(); r != nil {
			go ms.sendMetricFromChan(metricInfoChan)
		}
	}()

	ms.closeWG.Add(1)
	for {
		mc, ok := <-metricInfoChan
		if !ok {
			return
		}
		Counter(ms.name, mc.tags)
	}
}