使用 `github.com/go-playground/form/v4` 处理表单数据

package main

import (
	"fmt"
	"github.com/go-playground/form/v4"
	"net/http"
)

type User struct {
	Username string `form:"username"`
	Password string `form:"password"`
}

func main() {
	// 创建一个新的表单编解码器
	decoder := form.NewDecoder()

	// 模拟 HTTP 请求
	req, err := http.NewRequest("POST", "/login", nil)
	if err != nil {
		fmt.Println("Error creating request:", err)
		return
	}

	// 模拟表单数据
	req.PostForm = map[string][]string{
		"username": {"john_doe"},
		"password": {"secretpassword"},
	}

	// 创建一个 User 结构体实例
	var user User

	// 解码表单数据到结构体
	err = decoder.Decode(&user, req.PostForm)
	if err != nil {
		fmt.Println("Error decoding form:", err)
		return
	}

	// 打印解码后的数据
	fmt.Println("Username:", user.Username)
	fmt.Println("Password:", user.Password)
}