Fibonacci closure

/*
Exercise: Fibonacci closure
Let's have some fun with functions.

Implement a fibonacci function that returns a function (a closure) that returns successive fibonacci numbers (0, 1, 1, 2, 3, 5, ...).
*/

package main

import "fmt"

func fibonacci() func() int {
  before, val := 0, 1
  return func() int {
    ret := before
    before, val = val, before + val
    return ret
  }
}

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