The OnClosed handler is not called for all close states, the user it not always aware when the bind is closed.

In my case, I monitor OnClosed to give me the state of the bind, to either log or or change my metrics.
Possible fixes: Always return the state to the user, and let the user decide what to do with the closing state.

Related to the issue, there is no easy way for the user to verify the session state, it would be nice if the session had an accessor to get the current state.

Will provide PR this weekend.