学习Go语言中的网络编程函数并实现SMTP服务器发送邮件并记录日志？

package main

import (
    "log"
    "net/smtp"
)

func sendEmail() {
    // 邮件的发送者、接收者、主题和内容
    from := "sender@example.com"
    to := []string{"receiver1@example.com", "receiver2@example.com"}
    subject := "Hello, World!"
    body := "This is a test email."

    // SMTP服务器的地址和端口
    server := "smtp.example.com"
    port := 587

    // SMTP服务器的账号和密码
    username := "yourusername"
    password := "yourpassword"

    // 配置邮件的发送内容
    emailContent := []byte(
        "To: " + to[0] + "
" +
        "Subject: " + subject + "
" +
        "
" +
        body + "
",
    )

    // 连接到SMTP服务器
    auth := smtp.PlainAuth("", username, password, server)
    conn, err := smtp.Dial(server + ":" + string(port))
    if err != nil {
        log.Fatal(err)
    }

    // 登录认证
    if err := conn.Auth(auth); err != nil {
        log.Fatal(err)
    }

    // 设置邮件的发送者和接收者
    if err := conn.Mail(from); err != nil {
        log.Fatal(err)
    }
    for _, recipient := range to {
        if err := conn.Rcpt(recipient); err != nil {
            log.Fatal(err)
        }
    }

    // 发送邮件内容
    w, err := conn.Data()
    if err != nil {
        log.Fatal(err)
    }
    _, err = w.Write(emailContent)
    if err != nil {
        log.Fatal(err)
    }
    err = w.Close()
    if err != nil {
        log.Fatal(err)
    }

    // 关闭连接
    conn.Quit()

    // 记录日志
    log.Println("Email sent successfully!")
}

func main() {
    sendEmail()
}