If Close is called externally before a request is attempted, then we
will accidentally attempt to send to a closed channel, causing a panic.
To avoid this, we can check to see if Close has been called, using a
done channel. If this channel is ever done, we drop any incoming errors,
requests or pipes - we don't need them, since we're done.
Signed-off-by: Justin Chadwell <me@jedevc.com>
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