gorm 操作前后，更新参数

func (u *User) BeforeCreate(_ *gorm.DB) (err error) {

        u.Password = ScryptPw(u.Password)

        u.Role = 0

        return nil

 }

func (u *User) BeforeUpdate(_ *gorm.DB) (err error) {

        u.Password = ScryptPw(u.Password)

         return nil

}