var s = true
var host = "test_demo.qa_default.namingdns.com:9898"

func main() {
	dialer := &net.Dialer{
		Timeout:   30 * time.Second,
		KeepAlive: 30 * time.Second,
	}
	clt := &http.Client{
		Transport: &http.Transport{
			Proxy:           http.ProxyFromEnvironment,
			MaxIdleConns:    100,
			IdleConnTimeout: 30 * time.Second,
			DialContext: func(ctx context.Context, network, addr string) (conn net.Conn, err error) {
				return dialer.DialContext(ctx, "tcp4", addr)
			},
		}}
	file, err := os.OpenFile("run.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
	if err != nil {
		log.Fatal(err)
	}
	defer file.Close()

	log.SetOutput(file)
	for i := 0; i < 20; i++ {
		go func() {
			for {
				start := time.Now()
				if !s {
					continue
				}
				req, err := http.NewRequest("GET", "http://"+host, nil)
				trace := &httptrace.ClientTrace{
					DNSDone: func(info httptrace.DNSDoneInfo) {
						if info.Err != nil {
							log.Printf("DNS ERROR: %v, address: %+v\n", err, info)
						}
						timeCost := time.Now().Sub(start).Seconds()
						if timeCost > 5 {
							log.Printf("execute time more than 5s, %vs\n", timeCost)
						}
					},
				}
				req = req.WithContext(httptrace.WithClientTrace(req.Context(), trace))
				resp, err := clt.Do(req)
				if err != nil {
					log.Printf("%v\n", err)
				} else {
					resp.Body.Close()
				}
				time.Sleep(time.Millisecond * 100)
			}
		}()
	}
}