TUN-8817: Increase close session channel by one since there are two writers

When closing a session, there are two possible signals that will occur,
one from the outside, indicating that the session is idle and needs to
be closed, and the internal error condition that will be unblocked
with a net.ErrClosed when the connection underneath is closed. Both of
these routines write to the session's closeChan.

Once the reader for the closeChan reads one value, it will immediately
return. This means that the channel is a one-shot and one of the two
writers will get stuck unless the size of the channel is increased to
accomodate for the second write to the channel.

With the channel size increased to two, the second writer (whichever
loses the race to write) will now be unblocked to end their go routine
and return.

Closes TUN-8817

quic/v3/session.go

@@ -89,7 +89,10 @@ func NewSession(
 	log *zerolog.Logger,
 ) Session {
 	logger := log.With().Str(logFlowID, id.String()).Logger()
-	closeChan := make(chan error, 1)
+	// closeChan has two slots to allow for both writers (the closeFn and the Serve routine) to both be able to
+	// write to the channel without blocking since there is only ever one value read from the closeChan by the
+	// waitForCloseCondition.
+	closeChan := make(chan error, 2)
 	session := &session{
 		id:             id,
 		closeAfterIdle: closeAfterIdle,