implies observing the write to <code>a</code>.  This
version can (incorrectly) print an empty string
instead of <code>"hello, world"</code>.
</p>

<p>
Another incorrect idiom is busy waiting for a value, as in:
</p>

<pre>
var a string
var done bool

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

func main() {
	go setup()
	for !done {