[go-nuts] Once.Do

Hi,

As per the Go Memory Model (http://golang.org/ref/mem), the below code
should print "hello, world" twice. But I am not getting any output.
Can anyone let me know what I am missing?

package main

import "sync"
import "fmt"

var a string
var once sync.Once

func setup() {
a = "hello, world"
}

func doprint() {
once.Do(setup)
fmt.Println(a)
}

func twoprint() {
go doprint()
go doprint()
}

func main() {
twoprint()
}

http://play.golang.org/p/7yt6hXIZM4

Thanks