http://go-tour-jp.appspot.com/#44

go-tour-44.go

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func() int {

	n := 0
	a, b := 0, 1
	return func() int {
		fib := a + b
		switch n {
		case 0:
			fib = a
		case 1:
			fib = b
		default:
			a,b = b,fib
		}

		n++

		return fib
	}
}

func main() {
	f := fibonacci()
	for i := 0; i < 10; i++ {
		fmt.Println(f())
	}
}

result.txt

0
1
1
2
3
5
8
13
21
34

Program exited.