How to get particular fields in Preload while using Gorm - go

Question

I have two models which have many to many relations.
type User struct {
ID uint `gorm:"primary_key" json:"id"`
Name string `json:"name"`
Surname string `json:"surname"`
Email string `json:"email"`
Password string `json:"password"`
RoleID uint `json:"role_id"`
Classes []*Class `gorm:"many2many:user_classes;" json:"classes"`
CreatedAt time.Time `json:"created_at"`
UpdatedAt time.Time `json:"updated_at"`
}
type Class struct {
ID uint `gorm:"primary_key" json:"id"`
Name string `json:"name"`
Homeworks []Homework `gorm:"foreignKey:ClassID" json:"homeworks"`
Materials []Material `gorm:"foreignKey:ClassID" json:"materials"`
Users []*User `gorm:"many2many:classes;" json:"users"`
CreatedAt time.Time `json:"created_at"`
UpdatedAt time.Time `json:"updated_at"`
}
I want to get users with their classes but with only class id and class name. I did a lot of research and found this solution. However, it didn't work for me. I don't know why. Everything seems fine but didn't work.
My repository function's body is like that
var users []models.User
err := repo.db.Preload("Classes", func(db *gorm.DB) *gorm.DB {
return db.Select("ID", "Name")
}).Find(&users).Error
return users, err
I am expecting results like that
{
"id": 4,
"name": "Furkan",
"surname": "Topaloğlu",
"email": "furkantopalogluu#gmail.com",
"password": "fuki123",
"role_id": 2,
"classes": [
{
"id": 1,
"name": "IELTS Group 1"
},
{
"id": 2,
"name": "Speaking Club Grup 4"
}
],
"created_at": "2022-09-20T02:54:07.185756+03:00",
"updated_at": "2022-09-20T02:54:07.185756+03:00"
}
However, I'm getting this :
{
"id": 4,
"name": "Furkan",
"surname": "Topaloğlu",
"email": "furkantopalogluu#gmail.com",
"password": "fuki123",
"role_id": 2,
"classes": [
{
"id": 1,
"name": "IELTS Group 1",
"homeworks": null,
"materials": null,
"users": null,
"created_at": "0001-01-01T00:00:00Z",
"updated_at": "0001-01-01T00:00:00Z"
},
{
"id": 2,
"name": "Speaking Club Grup 4",
"homeworks": null,
"materials": null,
"users": null,
"created_at": "0001-01-01T00:00:00Z",
"updated_at": "0001-01-01T00:00:00Z"
}
],
"created_at": "2022-09-20T02:54:07.185756+03:00",
"updated_at": "2022-09-20T02:54:07.185756+03:00"
}
What am I doing wrong? Please help me.