purge outgoing segments when closing

kcp.go

@@ -1051,3 +1051,15 @@ func (kcp *KCP) remove_front(q []segment, n int) []segment {
 	}
 	return q[n:]
 }
+
+// Release all cached outgoing segments
+func (kcp *KCP) ReleaseTX() {
+	for k := range kcp.snd_queue {
+		xmitBuf.Put(kcp.snd_queue[k].data)
+	}
+	for k := range kcp.snd_buf {
+		xmitBuf.Put(kcp.snd_buf[k].data)
+	}
+	kcp.snd_queue = nil
+	kcp.snd_buf = nil
+}

sess.go

@@ -353,6 +353,8 @@ func (s *UDPSession) Close() error {
 		s.mu.Lock()
 		s.kcp.flush(false)
 		s.uncork()
+		// release pending segments
+		s.kcp.ReleaseTX()
 		s.mu.Unlock()
 
 		if s.l != nil { // belongs to listener