A Tour of Go 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.

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func() int {
    before :=
    now :=
    return func() int {
        if before ==  {
            before++
            return before
        }
        if now ==  {
            now++
            return now
        }
        temp := now
        now = before + now
        before = temp
        return now
    }
}

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