Session close timeout fails due to mixing relative and absolute times

[gmyers18]

The sent_close_time in WebSocket.State is an absolute epoch time (see line 240). But Session._check_close_timeout() performs a comparison which is based on elapsed seconds relative to the start of the session (see line 262), thus the close timeout will never fire. A simple fix would be to store "elapsed session time" in sent_close_time.

On a related note, it is a bit counter-intuitive to me that every call to WebSocket.close() updates the sent_close_time. Thus, for a case where multiple close packets happen to be sent, the close timeout check is always relative to the last packet rather than the first. If one is relying on the close timeout check to close out a session where the server fails to respond, and there is a programming error where close() is being called periodically in a loop, then the timeout will likely never succeed.

[willmcgugan]

Fixed in 0.2.2