s.TTFBAvgDuration = atomic.LoadUint64(&globalStats.tcpTimeForFirstByteTotalDur) / v
	}
	return s
}

// Return a function which update the global stats related to tcp connections
func setupReqStatsUpdate(req *http.Request) (*http.Request, func()) {
	var dialStart, dialEnd int64
	start := time.Now()
	trace := &httptrace.ClientTrace{
		GotFirstResponseByte: func() {

	if err != nil {
		return nil, &NetworkError{Err: err}
	}
	if length > 0 {
		req.ContentLength = length
	}

	_, expectTimeouts := ctx.Deadline()

	req, update := setupReqStatsUpdate(req)
	defer update()

	resp, err := c.httpClient.Do(req)
	if err != nil {
		if xnet.IsNetworkOrHostDown(err, expectTimeouts) {
			if !c.NoMetrics {
				atomic.AddUint64(&globalStats.errs, 1)
			}