[CHORE] refactor startGateway function to take callback.
[CHORE] refactor startGateway function to take callback.

crazyquark/gatewayd,xdv/gatewayd,Parkjeahwan/awegeeks,Parkjeahwan/awegeeks,whotooktwarden/gatewayd,zealord/gatewayd,crazyquark/gatewayd,zealord/gatewayd,xdv/gatewayd,whotooktwarden/gatewayd