</p>

<pre>
s[0] == 2
s[1] == 3
s[2] == 4
</pre>

<p>
For convenience, any of the indices may be omitted. A missing <code>low</code>
index defaults to zero; a missing <code>high</code> index defaults to the length of the
sliced operand:
</p>

<pre>
a[2:]  // same as a[2 : len(a)]
a[:3]  // same as a[0 : 3]
a[:]   // same as a[0 : len(a)]

	callbackMutex.Unlock()
}

//export goCallback
func goCallback(p unsafe.Pointer) {
	i := *(*int)(p)

	callbackMutex.Lock()
	f := callbackFuncs[i]
	callbackMutex.Unlock()

	if f == nil {
		panic("missing callback function")
	}
	f()
}

func testCallback(t *testing.T) {
	var x = false
	nestedCall(func() { x = true })
	if !x {
		t.Fatal("nestedCall did not call func")
	}
}