[Go] Closure demo.

package main

import (
    "log"
)

func num() func() int {
    n := -1

    return func() int {
        n += 1
        return n
    }
}

func main() {
    f := num()

    if !(f() == 0) {
        log.Fatal("Wrong number")
    }

    if !(f() == 1) {
        log.Fatal("Wrong number")
    }

    if !(f() == 2) {
        log.Fatal("Wrong number")
    }
}