Stateful Function

func powerOfTwo() func() int64 {
	x := 1.0
	return func() int64 {
		x++
		return int64(math.Pow(x, 2))
	}
}

Everytime the function is called, x is updated.

func main() {

	p2 := powerOfTwo()

	value := p2()
	fmt.Println(value) // 4

	value = p2()
	fmt.Println(value) // 9

	value = p2()
	fmt.Println(value) // 16
}