如何利用MySQL和Go语言开发一个简单的在线邮件系统

package main

import (
    "database/sql"
    "fmt"
    "log"
    "time"

    _ "github.com/go-sql-driver/mysql"
)

type Mail struct {
    MailID      int
    FromUserID  int
    ToUserID    int
    Subject     string
    Content     string
    SendTime    time.Time
}

func main() {
    db, err := sql.Open("mysql", "root:password@tcp(localhost:3306)/mail")
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    err = db.Ping()
    if err != nil {
        log.Fatal(err)
    }

    // 查询所有邮件
    rows, err := db.Query("SELECT * FROM mail")
    if err != nil {
        log.Fatal(err)
    }
    defer rows.Close()

    var mails []Mail

    for rows.Next() {
        var mail Mail
        err := rows.Scan(&mail.MailID, &mail.FromUserID, &mail.ToUserID, &mail.Subject, &mail.Content, &mail.SendTime)
        if err != nil {
            log.Fatal(err)
        }
        mails = append(mails, mail)
    }

    for _, mail := range mails {
        fmt.Println(mail)
    }
}

// 发送邮件
func SendMail(db *sql.DB, fromUserID int, toUserID int, subject string, content string) error {
    // TODO: 实现发送邮件的逻辑
}

// 接收邮件
func ReceiveMail(db *sql.DB, userID int) ([]Mail, error) {
    // TODO: 实现接收邮件的逻辑
}

// 删除邮件
func DeleteMail(db *sql.DB, mailID int) error {
    // TODO: 实现删除邮件的逻辑
}

func main() {
    db, err := sql.Open("mysql", "root:password@tcp(localhost:3306)/mail")
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    err = db.Ping()
    if err != nil {
        log.Fatal(err)
    }

    // 发送邮件
    err = SendMail(db, 1, 2, "Hello", "This is a test email.")
    if err != nil {
        log.Fatal(err)
    }

    // 接收邮件
    mails, err := ReceiveMail(db, 2)
    if err != nil {
        log.Fatal(err)
    }

    for _, mail := range mails {
        fmt.Println(mail)
    }

    // 删除邮件
    err = DeleteMail(db, 1)
    if err != nil {
        log.Fatal(err)
    }
}