How to develop a simple email management system using MySQL and Go language

CREATE TABLE `emails` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `subject` varchar(255) DEFAULT NULL,
  `sender` varchar(255) DEFAULT NULL,
  `receiver` varchar(255) DEFAULT NULL,
  `content` text,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

package main

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

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

type Email struct {
    ID       int
    Subject  string
    Sender   string
    Receiver string
    Content  string
}

func main() {
    // 连接到MySQL数据库
    db, err := sql.Open("mysql", "user:password@tcp(127.0.0.1:3306)/email_system")
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    // 发送邮件
    err = sendEmail(db, "Hello", "sender@example.com", "receiver@example.com", "This is the content of the email.")
    if err != nil {
        log.Fatal(err)
    }

    // 接收邮件
    emails, err := receiveEmails(db, "receiver@example.com")
    if err != nil {
        log.Fatal(err)
    }
    for _, email := range emails {
        fmt.Printf("Received email: Subject=%s, Sender=%s
", email.Subject, email.Sender)
    }

    // 查看邮件
    email, err := getEmail(db, 1)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("Email: Subject=%s, Sender=%s
", email.Subject, email.Sender)

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

// 发送邮件
func sendEmail(db *sql.DB, subject, sender, receiver, content string) error {
    _, err := db.Exec("INSERT INTO emails (subject, sender, receiver, content) VALUES (?, ?, ?, ?)",
        subject, sender, receiver, content)
    if err != nil {
        return err
    }
    return nil
}

// 接收邮件
func receiveEmails(db *sql.DB, receiver string) ([]Email, error) {
    rows, err := db.Query("SELECT * FROM emails WHERE receiver = ?", receiver)
    if err != nil {
        return nil, err
    }
    defer rows.Close()

    var emails []Email
    for rows.Next() {
        var email Email
        err := rows.Scan(&email.ID, &email.Subject, &email.Sender, &email.Receiver, &email.Content)
        if err != nil {
            return nil, err
        }
        emails = append(emails, email)
    }

    return emails, nil
}

// 查看邮件
func getEmail(db *sql.DB, id int) (Email, error) {
    var email Email
    err := db.QueryRow("SELECT * FROM emails WHERE id = ?", id).Scan(&email.ID, &email.Subject, &email.Sender, &email.Receiver, &email.Content)
    if err != nil {
        return Email{}, err
    }
    return email, nil
}

// 删除邮件
func deleteEmail(db *sql.DB, id int) error {
    _, err := db.Exec("DELETE FROM emails WHERE id = ?", id)
    if err != nil {
        return err
    }
    return nil
}