如何使用go-pg查询一对多关系

type User struct {
    ID     int
    Name   string
    Orders []*Order `pg:"rel:has-many"` // 定义一对多关系
}

type Order struct {
    ID     int
    UserID int
    User   *User `pg:"rel:has-one"` // 定义多对一关系
}

db := pg.Connect(&pg.Options{
    User:     "your_username",
    Password: "your_password",
    Database: "your_database",
})
defer db.Close()

var user User
err := db.Model(&user).
    Relation("Orders").
    Where("user.id = ?", userID).
    Select()
if err != nil {
    panic(err)
}

fmt.Println("User:", user.Name)
fmt.Println("Orders:")
for _, order := range user.Orders {
    fmt.Println("  -", order.ID)
}