Please help me to explain why this code fail, why on json result trip_from has empty string :

type Trip struct {
ID        int       `json:"id" gorm:"primary_key"`
Name      string    `json:"name"  gorm:"column:name"`
Estimate  int       `json:"estimate"  gorm:"column:estimate"`
Departure time.Time `json:"departure"  gorm:"column:departure"`
Price     int       `json:"price"  gorm:"column:price"`
Slot      int       `json:"slot"  gorm:"column:slot"`
FromId    int       `json:"from_id"  gorm:"column:from_id"`
TripFrom  string    `json:"trip_from" gorm:"column:trip_from"`
ToId      int       `json:"to_id"  gorm:"column:to_id"`
To        string    `json:"trip_to"  gorm:"-"`
Thumbnail string    `json:"thumbnail"  gorm:"column:thumbnail"`
Slug      string    `json:"slug"  gorm:"column:slug"`
CreatedAt time.Time `json:"created_at"`
UpdatedAt time.Time `json:"updated_at"`
}

var trips []model.Trip
err := e.DB.Debug().
    Select("trips.*, cities.name  as trip_from").
    Joins("JOIN cities ON cities.id = trips.from_id").
    Where("trips.id = ?", "1").
    Find(&trips)
if err.Error != nil {
    helper.CommonLogger().Error(err)
    fmt.Printf("[tripRepository.ReadAll] error execute query %v n", err)
    return nil, fmt.Errorf("failed view all data")
}
fmt.Println(trips)
return &trips, nil

Why json result trip_from return empty string