golang邮箱发送验证码

常用邮箱：
QQ 邮箱
POP3 服务器地址：qq.com（端口：995）
SMTP 服务器地址：smtp.qq.com（端口：465/587）

163 邮箱：
POP3 服务器地址：pop.163.com（端口：110）
SMTP 服务器地址：smtp.163.com（端口：25）

126 邮箱：
POP3 服务器地址：pop.126.com（端口：110）
SMTP 服务器地址：smtp.126.com（端口：25）
代码如下：
首先导入包：

"net/smtp"
"math/rand"//随机数
"time"
"fmt"
"log"

定义一个Map存放邮箱号及对应随机码

var Code = make(map[string]int) //key为Email,value为随机码

邮箱发送验证码

func SendEmail(email string) int {
     //smtp.PlainAuth()
     // 参数1：Usually identity should be the empty string, to act as username
     // 参数2：username
    //参数3：password
    //参数4：host
	auth := smtp.PlainAuth("", "[e-mail]", "此处填写邮箱密码", "smtp.163.com")
	to := []string{"[e-mail]"}
	//发送随机数为验证码
	// Seed uses the provided seed value to initialize the default Source to a
	// deterministic state. If Seed is not called, the generator behaves as
	// if seeded by Seed(1). Seed values that have the same remainder when
	// divided by 2^31-1 generate the same pseudo-random sequence.
	// Seed, unlike the Rand.Seed method, is safe for concurrent use.
	rand.Seed(time.Now().Unix())
	// Intn returns, as an int, a non-negative pseudo-random number in [0,n)
	num := rand.Intn(10000)
	//发送内容使用base64 编码，单行不超过80字节，需要插入\r\n进行换行
	//The msg headers should usually include
	// fields such as "From", "To", "Subject", and "Cc".  Sending "Bcc"
	// messages is accomplished by including an email address in the to
	// parameter but not including it in the msg headers.
	str := fmt.Sprintf("From:[e-mail]\r\nTo:[e-mail]\r\nSubject:verifycode\r\n\r\n,%d,\r\n.", num)//邮件格式
	msg := []byte(str)
	err := smtp.SendMail("smtp.163.com:25", auth, "[e-mail]", to, msg)
	if err != nil {
		log.Fatal(err)
	}
	return num
}