JavaScript async function not executed in module

According to the compatibility table, Firefox 54 supports async/await but in the following code, the asynchronous function never gets executed, even though it does not even wait for anything. Is the compatibility table wrong or is there a mistake in the code?

<html>
<body>
<script type="module">
function helloSync()
{
 alert("sync: This alert always happens");
}

async function helloAsync()
{
 alert("async: This alert never happens");
}

helloSync();
helloAsync();
</script>
</body>
</html>