ex7.go

package ecommerce

import (
	"strconv"
)

type order struct {
	pid productID
	cid customerID
}

type productID int64


// some methods on productID type

type customerID int64

// some methods on customerID type

type orderID int64

func (oid orderID) String() string {
	return strconv.FormatInt(int64(oid), 10)
}

// some other methods on orderID type

func CreateOrder(pid int64, cid int64) order {
	return order{
		pid: productID(pid), cid: customerID(cid),
	}
}

func (o order) Submit() (orderID, error) {
	// do some logic

	return orderID(int64(3252345234)), nil
}