如何从另一个包中添加gorm中的默认值

package models

type User struct {
    ID       uint   `gorm:"primary_key"`
    Username string `gorm:"default:'guest'"`
    Email    string `gorm:"default:''"`
}

package main

import (
    "fmt"
    "github.com/your-username/project/models"
    "gorm.io/driver/mysql"
    "gorm.io/gorm"
)

func main() {
    dsn := "user:password@tcp(127.0.0.1:3306)/database?charset=utf8mb4&parseTime=True&loc=Local"
    db, err := gorm.Open(mysql.Open(dsn), &gorm.Config{})
    if err != nil {
        panic("failed to connect database")
    }

    // 自动迁移模式
    db.AutoMigrate(&models.User{})

    // 创建用户
    user := models.User{}
    db.Create(&user)

    fmt.Println(user.Username) // 输出: guest
    fmt.Println(user.Email)    // 输出: 空字符串
}