using smart select in gorm with many 2 many relation - go

Question

I want to use smart select when querying rooms table. When use the original struct it works fine but when use smart select it fails.
Here is my schema
type Room struct {
gorm.Model
ID uint `json:"id" gorm:"primary_key"`
Hash string `json:"hash" binding:"required" gorm:"not null:true"`
Users []User `json:"users" gorm:"many2many:room_users"`
Messages []Message `json:"messages"`
}
type RoomAPI struct {
ID uint `json:"id" gorm:"primary_key"`
Hash string `json:"hash" binding:"required" gorm:"not null:true"`
Users []User `json:"users" gorm:"many2many:room_users"`
//Messages []Message `json:"messages" gorm:"foreignKey:RoomID"`
}
func (RoomAPI) TableName() string {
return "rooms"
}
type User struct {
gorm.Model
ID uint `json:"id" gorm:"primary_key"`
Name string `json:"name" binding:"required" gorm:"not null:true"`
Phone string `json:"phone"`
Email string `json:"email" binding:"required,email" gorm:"not null:true"`
Password string `json:"password" binding:"required,min=8" gorm:"not null:true"`
Gender string `json:"gender" binding:"Enum=male_female" gorm:"type:gender;not null:true;default:male"`
Rooms []Room `json:"rooms" gorm:"many2many:room_users"`
}
type Message struct {
gorm.Model
ID uint `json:"id" gorm:"primary_key"`
Text string `json:"text" binding:"required" gorm:"not null:true"`
UserID uint `json:"user_id" gorm:"not null:true"`
RoomID uint `json:"room_id" gorm:"not null:true"`
}
here is my query
var rooms []RoomAPI
user := User{ID: userId}
err := db.DB.Model(&user).Preload("Users").
Association("Rooms").
Find(&rooms)
if err != nil {
log.Printf("err -> %+v", err)
return err, nil
}
return nil, rooms
I want to get rooms with selected fields with smart select but it fails