<p>
If the map or slice is <code>nil</code>, <code>clear</code> is a no-op.
</p>


<h3 id="Close">Close</h3>

<p>
For a channel <code>ch</code>, the built-in function <code>close(ch)</code>
records that no more values will be sent on the channel.
It is an error if <code>ch</code> is a receive-only channel.
Sending to or closing a closed channel causes a <a href="#Run_time_panics">run-time panic</a>.