Fix panic on Ping/WriteMessage for webtorrent

Introduced in anacrolix/torrent #455

diff --git a/webtorrent/tracker_client.go b/webtorrent/tracker_client.go
index c5aacaf25f36b7234d95fba430757bf48a29cbfb..0fe980c7a21c77b3ae11ad9f89f6c2f2ed353099 100644 (file)
--- a/webtorrent/tracker_client.go
+++ b/webtorrent/tracker_client.go
@@ -84,7 +84,9 @@ func (tc *TrackerClient) doWebsocket() error {
                for {
                        select {
                        case <-tc.pingTicker.C:
+                               tc.mu.Lock()
                                err := c.WriteMessage(websocket.PingMessage, []byte{})
+                               tc.mu.Unlock()
                                if err != nil {
                                        return
                                }