Hey, thanks for maintaining this library!

I apologize because this is not a good bug report. I don't have logs or a reproducible example. But I ran into an issue once that I cannot reproduce now and I think I tracked it down to possible race conditions in WebSocketApp.

I see WebSocketApp.run_forever() and WebSocketApp.close() both mutate self.sock and self.keep_running. So when calling them from different threads, those calls might interleave and produce data races, where the socket is not properly closed.

I'm pretty sure that's the issue I saw. Again, apologies for no concrete examples, but I thought it would be worth bringing this to your attention!