Gorm Can I use Preload With Scan?

Your Question

Let's say I have two tables test_user and language, and a many-to-many table test_user_language

type TestUser struct {
    ID        string     `json:"id" gorm:"primaryKey"`
    Languages []Language `gorm:"many2many:test_user_language"` 
    Base
}

type Language struct {
    ID   string `json:"id" gorm:"primaryKey"`
    Name string `json:"name"`
    Base
}

I tried to use Preload and Scan together. Like below:

func main(){
cfg, _ := config.Load()

    db, _ := dbutil.New(cfg.DbDsn, cfg.DbLog)
    var err error
    r := []*model.TestUser{}
    err = db.Model(&model.TestUser{}).
        Preload("Languages").Scan(&r).Error
    if err != nil {
        panic(err)
}

It seemed not to work. But it worked if I replaced Scan() with Take() or Find(). Can anyone tell me why? I have searched for this but didn't find any document or explanation for this. All the answers would be appreciated! Many thanks 🙏

The document you expected this should be explained

Expected answer