im a beginner in golang. when im using gorm:"primaryKey" 
i dont see any field that use primary key
this is my model
type Orders struct {
OrderID uint64 `gorm:"primaryKey" json:"orderId"`
CustomerName string `json:"customerName"`
OrderedAt time.Time `json:"orderedAt" example:"2020-01-09T21:21:46+00:00"`
Items []Items `json:"items"`
}
type Items struct {
ItemID uint64 `gorm:"primaryKey" json:"lineItemId"`
Item_code string `json:"itemCode"`
Description string `json:"description"`
Quantity int `json:"quantity"`
}
which part do i wrong? and do i need relational database for items field?