The third parameter passed to PeerServer or ExpressPeerServer can
optionally be a function that returns any string value, which will be
used as the client ID. Checking whether the ID is already taken is not
to be handled by the function.
For instance:
ExpressPeerServer(,,() => {
return 'abc';
})
1.register router path duplicate in 'init' function(line 16) and 'PeerServer' function (line 109)
2.app.mountpath is undefined. It will make WebSocketServer.constructor lost router path.
