#f is passed), on the default event
loop.
</p>
<p>In practice, calling await-sleep! may often be more convenient for
composing asynchronous code than using this procedure.  That is
because, when &rsquo;thunk&rsquo; is executed, this procedure is waiting on
&rsquo;await&rsquo;, so &rsquo;await&rsquo; and &rsquo;resume&rsquo; cannot be used again in &rsquo;thunk&rsquo;
(although &rsquo;thunk&rsquo; can call a-sync to start another series of
asynchronous operations with a new await-resume pair).  In retrospect