convert interface to type golang code example

Example 1: golang convert interface to concrete type

type Person struct {
	firstName string
	lastName  string
}
func printIfPerson(object interface{}) {
	person, ok := object.(Person)
	if ok {
		fmt.Printf("Hello %s!\n", person.firstName)
	}
}

Example 2: interface to int golang

iAreaId := val.(int)
iAreaId, ok := val.(int) // Alt. non panicking version