Golang网站开发与重定向问题求助

我复刻了你的仓库，并添加了一个用于跟踪用户的示例Cookie，地址如下：

我将数据库替换为了硬编码的用户。

看了你的代码，重定向问题主要出现在BookingHandler函数中。问题在于checkLogin函数的设计方式，它总是从请求中读取表单值，但访问/Booking页面时并没有提交表单数据。

以下是修复后的代码：

package main

import (
    "database/sql"
    "encoding/json"
    "fmt"
    "io/ioutil"
    "log"
    "net/http"
    "os"
    "time"

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

type DatabaseConfig struct {
    Username string `json:"user"`
    Password string `json:"password"`
    Host     string `json:"host"`
    Port     int    `json:"port"`
    Database string `json:"dbname"`
}

var dbc string
var db *sql.DB

func logError(err error) {
    if err != nil {
        log.Println(err)
    }
}

func main() {
    logFile, err := os.OpenFile("errors.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
    if err != nil {
        log.Println(err)
    }
    defer logFile.Close()

    log.SetOutput(logFile)

    // read json file
    configBytes, err := ioutil.ReadFile("Db.json")
    if err != nil {
        logError(err)
    }

    // setting up new struct
    var config DatabaseConfig
    if err := json.Unmarshal(configBytes, &config); err != nil {
        log.Println(err)
    }

    // make connection database
    dbc = fmt.Sprintf("%s:%s@tcp(%s:%d)/%s", config.Username, config.Password, config.Host, config.Port, config.Database)
    db, err = sql.Open("mysql", dbc)
    if err != nil {
        logError(err)
    }
    defer db.Close()

    if err := db.Ping(); err != nil {
        log.Println(err)
    }

    mux := http.NewServeMux()
    mux.HandleFunc("/", RootHandler)
    mux.HandleFunc("/Locatie", LocatieHandler)
    mux.HandleFunc("/Login", LoginHandler)
    mux.HandleFunc("/Booking", BookingHandler)
    mux.HandleFunc("/Logout", LogoutHandler)

    http.ListenAndServe(":8080", mux)
}

func checkLogin(r *http.Request) (bool, int) {
    // get session cookie
    sessionCookie, err := r.Cookie("session_id")
    if err != nil {
        return false, 0
    }

    // check if session exists and is valid
    var userID int
    var endTime time.Time
    err = db.QueryRow("SELECT user_id, end_time FROM sessions WHERE session_id = ?", sessionCookie.Value).Scan(&userID, &endTime)
    if err != nil {
        return false, 0
    }

    // check if session is still valid
    if time.Now().After(endTime) {
        return false, 0
    }

    return true, userID
}

func RootHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintln(w, `        <h1>Fonteyn Vakantieparken</h1>         <p>Vakantie parken voor een onvergeetelijke vakantie.</p>         <ul>             <li><a href="/Locatie">Locatie</a></li>             <li><a href="/Login">Login</a></li>         </ul>     `)
}

func LocatieHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintln(w, `        <h1>Locatie</h1>         <p>Wij zijn beschikbaar in meerder landen.</p>         <ul>             <li><a href="/">Home</a></li>             <li><a href="/Login">Login</a></li>         </ul>     `)
}

func BookingHandler(w http.ResponseWriter, r *http.Request) {
    // Check if user is logged in using session
    loggedIn, userID := checkLogin(r)
    if !loggedIn {
        http.Redirect(w, r, "/Login", http.StatusSeeOther)
        return
    }

    // Display booking page for logged in user
    fmt.Fprintf(w, `        <h1>Booking Page</h1>         <p>Welcome, User ID: %d</p>         <p>This is the booking page.</p>         <ul>             <li><a href="/">Home</a></li>             <li><a href="/Logout">Logout</a></li>         </ul>     `, userID)
}

func LoginHandler(w http.ResponseWriter, r *http.Request) {
    // If already logged in, redirect to booking page
    loggedIn, _ := checkLogin(r)
    if loggedIn {
        http.Redirect(w, r, "/Booking", http.StatusSeeOther)
        return
    }

    if r.Method == "GET" {
        fmt.Fprintln(w, `        <h1>Fonteyn Vakantieparken</h1>         <h2>Inloggen</h2>         <form action="/Login" method="POST">             <label for="username">Gebruikersnaam:</label><br>             <input type="text" id="username" name="username"><br>             <label for="password">Wachtwoord:</label><br>             <input type="password" id="password" name="password"><br><br>             <input type="submit" value="Inloggen">         </form>    `)
    } else if r.Method == "POST" {
        username := r.FormValue("username")
        password := r.FormValue("password")

        // Execute a SELECT query to check if the username and password are correct
        var userID int
        err := db.QueryRow("SELECT id FROM users WHERE username=? AND password=?", username, password).Scan(&userID)
        if err != nil {
            fmt.Fprintln(w, "Invalid username or password.")
            fmt.Fprintln(w, `<a href="/Login">Try again</a>`)
            return
        }

        // Create session
        var sessionID string
        err = db.QueryRow("INSERT INTO sessions (user_id, start_time, end_time) VALUES (?, NOW(), DATE_ADD(NOW(), INTERVAL 1 HOUR)) RETURNING session_id", userID).Scan(&sessionID)
        if err != nil {
            // If RETURNING is not supported, use alternative approach
            result, err := db.Exec("INSERT INTO sessions (user_id, start_time, end_time) VALUES (?, NOW(), DATE_ADD(NOW(), INTERVAL 1 HOUR))", userID)
            if err != nil {
                fmt.Fprintln(w, "Session creation failed.")
                return
            }
            
            sessionIDInt, _ := result.LastInsertId()
            sessionID = fmt.Sprintf("%d", sessionIDInt)
        }

        // Set session cookie
        http.SetCookie(w, &http.Cookie{
            Name:     "session_id",
            Value:    sessionID,
            Expires:  time.Now().Add(1 * time.Hour),
            HttpOnly: true,
        })

        http.Redirect(w, r, "/Booking", http.StatusSeeOther)
    }
}

func LogoutHandler(w http.ResponseWriter, r *http.Request) {
    // Clear session cookie
    http.SetCookie(w, &http.Cookie{
        Name:     "session_id",
        Value:    "",
        Expires:  time.Now().Add(-1 * time.Hour),
        HttpOnly: true,
    })
    
    http.Redirect(w, r, "/", http.StatusSeeOther)
}

主要修改：

1. 将数据库连接设为全局变量，避免重复连接
2. 修改checkLogin函数使用会话cookie验证，而不是每次都检查表单数据
3. 在登录成功后创建会话记录并设置cookie
4. 添加会话过期时间（1小时）
5. 添加登出功能
6. 修改数据库sessions表结构，需要添加session_id字段和end_time字段

需要更新数据库sessions表：

ALTER TABLE sessions ADD COLUMN session_id INT AUTO_INCREMENT PRIMARY KEY;
ALTER TABLE sessions ADD COLUMN end_time DATETIME;

这样修改后，登录流程会正常工作，重定向到预订页面也会按预期执行。