[Go] Send SMS message with CoolSMS API

coolsms_send_sms.go

package main

import (
	"crypto/hmac"
	"crypto/md5"
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"strconv"
	"time"
)

// put your api key and secret
// https://www.coolsms.co.kr/index.php?mid=service_setup&act=dispSmsconfigCredential
const (
	apiKey    = ""
	apiSecret = ""
)

func sendSMS(to, from, text string) (bool, error) {
	var b []byte

	// get unix timestamp
	ts := strconv.Itoa(int(time.Now().Unix()))

	// generate salt (length of 5~30)
	b = make([]byte, 30)
	if _, err := rand.Read(b); err != nil {
		return false, err
	}
	salt := string(b)

	// HMAC hash
	h := hmac.New(md5.New, []byte(apiSecret))
	h.Write([]byte(ts + salt))
	sig := hex.EncodeToString(h.Sum(nil))

	// call API
	data := url.Values{
		// authentication information
		"api_key":   {apiKey},
		"timestamp": {ts},
		"salt":      {salt},
		"signature": {sig},

		// send parameters
		"to":   {to},
		"from": {from},
		"text": {text},
	}
	resp, err := http.PostForm("https://api.coolsms.co.kr/sms/2/send", data)
	if err != nil {
		return false, err
	}
	defer resp.Body.Close()

	var r struct {
		GroupID      string `json:"group_id"`
		SuccessCount int    `json:"success_count"`
		ErrorCount   int    `json:"error_count"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&r); err != nil {
		return false, err
	}
	if r.SuccessCount == 0 {
		return false, errors.New("sms send failed")
	}

	return true, nil
}

func main() {
	// sender's phone number must be registered first
	// https://www.coolsms.co.kr/index.php?mid=service_setup&act=dispSmsconfigSenderNumbers
	fmt.Println(sendSMS("sms to", "sms from", "content"))
}