</p>

<pre>
var a string
var done bool

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

func doprint() {
	if !done {
		once.Do(setup)
	}
	print(a)
}

func twoprint() {
	go doprint()
	go doprint()
}
</pre>

<p>
but there is no guarantee that, in <code>doprint</code>, observing the write to <code>done</code>

the function argument <code>g</code> and protects callers from
run-time panics raised by <code>g</code>.
</p>

<pre>
func protect(g func()) {
	defer func() {
		log.Println("done")  // Println executes normally even if there is a panic
		if x := recover(); x != nil {
			log.Printf("run time panic: %v", x)
		}
	}()
	log.Println("start")
	g()
}
</pre>

the function argument <code>g</code> and protects callers from
run-time panics raised by <code>g</code>.
</p>

<pre>
func protect(g func()) {
	defer func() {
		log.Println("done")  // Println executes normally even if there is a panic
		if x := recover(); x != nil {
			log.Printf("run time panic: %v", x)
		}
	}()
	log.Println("start")
	g()
}
</pre>