package main
 
import (
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"strconv"
	"strings"
	"time"
)
 
func connHandler(w http.ResponseWriter, r *http.Request) {
	// parse
	r.ParseForm()
	response_time := r.Header.Get("sleep-time")
	// = NOTE
	if _, err := ioutil.ReadAll(r.Body); err != nil {
		http.Error(w, err.Error(), 500)
		return
	}
	defer r.Body.Close()
	// sleep for some time
	resp_time := 1
	if response_time != "" {
		ms, _ := strconv.ParseFloat(response_time, 64)
		resp_time = (int)(ms * 1000)
	}
	time.Sleep(time.Duration(resp_time) * time.Millisecond)
	// parepare response
	status := 200
	body := ""
	w.Header().Set("Content-Type", "text/plain")
	w.Header().Set("Content-Length", strconv.Itoa(len(body)))
	w.WriteHeader(status)
	w.Write([]byte(body))
}
 
func main() {
	http.HandleFunc("/", connHandler)
	if err := http.ListenAndServe(":server_port", nil); err != nil {
		log.Fatal("ListenAndServe: ", err)
	}
}

package main

import (
  "bytes"
  "fmt"
  "io"
  "io/ioutil"
  "log"
  "net/http"
  "time"
)

var (
  httpClient *http.Client
)

const (
  MaxIdleConnections int = 20
  RequestTimeout   int = 30
)

// init HTTPClient
func init() {
  httpClient = createHTTPClient()
}

// createHTTPClient for connection re-use
func createHTTPClient() *http.Client {
  client := http.Client{
   Transport: http.Transport{
      MaxIdle  ConnsPerHost: MaxIdleConnections,
 },
 Timeout: time.Duration(RequestTimeout) * time.Second,
  }
  return client
}

func conn_reuse_post(conn_reuse_times int) {
  var endPoint string = "http://server_ip:server_port/"
  data := []byte{}
  // fill data 
  for i := 0; i  conn_reuse_times; i++ {
 // use global httpClient to send request
 resp, err := httpClient.Post(endPoint, "application/x-www-form-urlencoded", bytes.NewBuffer([]byte(data)))
 fmt.Println(resp)
 if err != nil {
   log.Println("err", err)
   return
 }
 io.Copy(ioutil.Discard, resp.Body) // = NOTE
 resp.Body.Close()  // = NOTE
  }
}

func main() {
  conn_reuse_post(5)
}