1、http.NewRequest()

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"unsafe"
)

type JsonPostSample struct {
}

func (this *JsonPostSample) SamplePost() {
	info := make(map[string]string)    
	info["username"] = "******"
	info["password"] = "******"

	bytesData, err := json.Marshal(info)
	if err != nil {
		fmt.Println(err.Error())
		return
	}
	fmt.Println(bytesData)

	reader := bytes.NewReader(bytesData)
	

	url := "http://xxxxxxxx.com"     //要访问的Url地址
	request, err := http.NewRequest("POST", url, reader)
	defer request.Body.Close()    //程序在使用完回复后必须关闭回复的主体
	if err != nil {
		fmt.Println(err.Error())
		return
	}
	request.Header.Set("Content-Type", "application/json;charset=UTF-8")   
	//必须设定该参数,POST参数才能正常提交，意思是以json串提交数据
	
	client := http.Client{}
	resp, err := client.Do(request) //Do 方法发送请求，返回 HTTP 回复
	if err != nil {
		fmt.Println("22222", err.Error())
		return
	}

	respBytes, err := ioutil.ReadAll(resp.Body)   
	if err != nil {
		fmt.Println("33333", err.Error())
		return
	}

	//byte数组直接转成string，优化内存
	str := (*string)(unsafe.Pointer(&respBytes))
	fmt.Println("44444", *str)

	//fmt.Println(string(respBytes))
}

func main() {
	a := new(JsonPostSample)
	a.SamplePost()

}

参考资料：https://blog.csdn.net/chenghuan1990/article/details/75426066

获取状态码，包头信息等：https://juejin.im/post/5ce242c2f265da1b6e6574de

2、http.Post()

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
)

func main() {
	song := make(map[string]string)
	song["username"] = "******"
	song["password"] = "******"
	bytesData, _ := json.Marshal(song)

	res, err := http.Post("http://xxxxxx.com",
		"application/json;charset=utf-8", bytes.NewBuffer([]byte(bytesData)))
	if err != nil {
		fmt.Println("Fatal error ", err.Error())
	}

	defer res.Body.Close()

	content, err := ioutil.ReadAll(res.Body)
	if err != nil {
		fmt.Println("Fatal error ", err.Error())
	}

	//fmt.Println(string(content))
	str := (*string)(unsafe.Pointer(&content)) //转化为string,优化内存
	fmt.Println(*str)
}

参考资料：https://www.kancloud.cn/digest/batu-go/153529