// Return a function which update the global stats related to tcp connections
func setupReqStatsUpdate(req *http.Request) (*http.Request, func()) {
	var dialStart, dialEnd int64

	trace := &httptrace.ClientTrace{
		ConnectStart: func(network, addr string) {
			atomic.StoreInt64(&dialStart, time.Now().UnixNano())
		},
		ConnectDone: func(network, addr string, err error) {
			if err == nil {
				atomic.StoreInt64(&dialEnd, time.Now().UnixNano())