o file, which cannot be marshalled.</span>
(<span class="mdzsyn-coresym">thread/new</span> <span class="mdzsyn-symbol">worker</span>)</code></pre><p>The fix here is to move the file creation inside the worker function, since
every worker thread is going to have its own copy of the file handle.
</p>
<pre class="mendoza-codeblock"><code data-language="janet">(<span class="mdzsyn-coresym">defn</span> <span class="mdzsyn-symbol">worker</span>
  [<span class="mdzsyn-symbol">parent</span>]
  (<span class="mdzsyn-