如何在Golang中实现Web表单自动校验

type UserForm struct {
    Username string `schema:"username" validate:"required,min=3,max=20"`
    Email    string `schema:"email"    validate:"required,email"`
    Age      int    `schema:"age"      validate:"gte=0,lte=120"`
}

func handleForm(w http.ResponseWriter, r *http.Request) {
    if r.Method != "POST" {
        // 渲染表单页面
        return
    }

    var form UserForm
    decoder := schema.NewDecoder()
    err := decoder.Decode(&form, r.PostForm)
    if err != nil {
        http.Error(w, "解析表单失败", 400)
        return
    }

    // 使用 validator 校验
    validate := validator.New()
    err = validate.Struct(form)
    if err != nil {
        // 处理校验错误
        for _, e := range err.(validator.ValidationErrors) {
            fmt.Fprintf(w, "字段 %s 错误: %s\n", e.Field(), e.Tag())
        }
        return
    }

    // 校验通过，处理业务逻辑
    fmt.Fprintln(w, "提交成功")
}

func bindAndValidate(r *http.Request, dst interface{}) error {
    if err := r.ParseForm(); err != nil {
        return err
    }

    decoder := schema.NewDecoder()
    decoder.IgnoreUnknownKeys(true)
    if err := decoder.Decode(dst, r.PostForm); err != nil {
        return err
    }

    validate := validator.New()
    return validate.Struct(dst)
}

var form UserForm
if err := bindAndValidate(r, &form); err != nil {
    // 返回错误信息
    return
}

validate.RegisterValidation("phone", func(fl validator.FieldLevel) bool {
    phone := fl.Field().String()
    // 简单正则匹配中国手机号
    return regexp.MustCompile(`^1[3-9]\d{9}$`).MatchString(phone)
})

Phone string `schema:"phone" validate:"required,phone"`

type FormResponse struct {
    Form   interface{}
    Errors map[string]string
}