Some thoughts on possible refactorings
- Use Msg or Message (I would go for Msg) consistently, e.g. MsgWithResponse and MessageWithAction
- Shouldn't it be called WorkerMaster instead of WorkMaster?
- LocalWorkMaster defines some methods that take an IdType, e.g. unfreeze: These parameters should be named id, not key
- Wouldn't it make sense to implement LocalWorkMaster.idType and WorkerId.myType?
