Gorm example of foreign key definition for a hasMany relation

hasMany.go

package main

import (
	"fmt"
	"github.com/jinzhu/gorm"
	_ "github.com/jinzhu/gorm/dialects/postgres"
)

// Customer ...
type Customer struct {
	CustID       int `gorm:"primary_key"`
	CustomerName string
	Contacts     []Contact `gorm:"ForeignKey:CustID"`
}

// Contact ...
type Contact struct {
	ContactID   int `gorm:"primary_key"`
	CountryCode int
	MobileNo    uint
	CustID      int
}

func main() {
	db, err := gorm.Open("postgres", "user=intercloud password=intercloud dbname=intercloud sslmode=disable")
	if err != nil {
		panic(err.Error())
	}
	defer db.Close()
	db.DropTableIfExists(&Contact{}, &Customer{})
	db.AutoMigrate(&Customer{}, &Contact{})
	db.Model(&Contact{}).AddForeignKey("cust_id", "customers(cust_id)", "CASCADE", "CASCADE")

	/* Here, I'm manually adding foreign key. It is not creating by GORM even if I write tag
	   `gorm:"ForeignKey:CustID"` in struct model  as I have written in Customer struct    */

	Custs1 := Customer{CustomerName: "John", Contacts: []Contact{
		{CountryCode: 91, MobileNo: 956112},
		{CountryCode: 91, MobileNo: 997555}}}

	Custs2 := Customer{CustomerName: "Martin", Contacts: []Contact{
		{CountryCode: 90, MobileNo: 808988},
		{CountryCode: 90, MobileNo: 909699}}}
	db.Create(&Custs1)
	db.Create(&Custs2)

	cust := []Customer{}
	db.Debug().Where("customer_name=?", "Martin").Preload("Contacts").Find(&cust)

	fmt.Println(cust)
}