# wait 2 seconds before canceling the long IO.</span>
(<span class="mdzsyn-coresym">ev/sleep</span> <span class="mdzsyn-number">2</span>)
(<span class="mdzsyn-coresym">ev/cancel</span> <span class="mdzsyn-symbol">f</span> <span class="mdzsyn-string">"canceled"</span>)</code></pre><h2 id="Supervisor-Channels">Supervisor Channels
</h2>
<p>An interesting problem with supporting multiple tasks is error handling - if a task raises an error (or any other uncaught signal), who should handle it? The programmer
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