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

	// Pass the address of i because the C function was written to
	// take a pointer.  We could pass an int if we felt like
	// rewriting the C code.
	C.callback(unsafe.Pointer(&i))

	callbackMutex.Lock()
	delete(callbackFuncs, i)
	callbackMutex.Unlock()
}

//export goCallback

spaces) and may also exclude the characters
<code>!"#$%&amp;'()*,:;&lt;=&gt;?[\]^`{|}</code>
and the Unicode replacement character U+FFFD.
</p>

<p>
Assume we have compiled a package containing the package clause
<code>package math</code>, which exports function <code>Sin</code>, and
installed the compiled package in the file identified by
<code>"lib/math"</code>.