<p>
Even if <code>main</code> observes <code>g != nil</code> and exits its loop,
there is no guarantee that it will observe the initialized
value for <code>g.msg</code>.
</p>

<p>
In all these examples, the solution is the same:
use explicit synchronization.
</p>

<h2 id="badcompiler">Incorrect compilation</h2>

<p>
The Go memory model restricts compiler optimizations as much as it does Go programs.