プログラム

http_post.go

// ---------------------------------------------------------------
//
//	http_post.go
//
//					Feb/24/2020
// ---------------------------------------------------------------
package main

import (
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"
)

// ---------------------------------------------------------------
func main() {
	fmt.Printf ("*** 開始 ***\n")
	url_target := "https://httpbin.org/post"
	args := url.Values{}
	args.Add("user","jiro")
	args.Add("password","123456")
	res, err := http.PostForm(url_target,args)
	if err != nil {
		fmt.Println("Request error:", err)
		return
	}
	defer res.Body.Close()

	body, err := ioutil.ReadAll(res.Body)
	if err != nil {
		fmt.Println("Request error:", err)
		return
	}

	str_json := string(body)
	fmt.Println(str_json)

	fmt.Printf ("*** 終了 ***\n")
}

// ---------------------------------------------------------------

実行結果

$ go run http_post.go
*** 開始 ***
{
  "args": {}, 
  "data": "", 
  "files": {}, 
  "form": {
    "password": "123456", 
    "user": "jiro"
  }, 
  "headers": {
    "Accept-Encoding": "gzip", 
    "Content-Length": "25", 
    "Content-Type": "application/x-www-form-urlencoded", 
    "Host": "httpbin.org", 
    "User-Agent": "Go-http-client/2.0", 
    "X-Amzn-Trace-Id": "Root=1-5e532ac5-3fd72da01bd57240d7b094c8"
  }, 
  "json": null, 
  "origin": "163.49.213.57", 
  "url": "https://httpbin.org/post"
}

*** 終了 ***

確認したバージョン

$ go version
go version go1.19.2 linux/amd64