StartWorkerService starts the event queue listener service to listen for configured events return channel to track the finish event to wait sync for the service to finish: fc, err := StartWorkerService(data) handle err <-fc // waits for finish.

ServiceData keeps data required for service work.

EmailMaker prepares the email.

EmailRetriever return the email by ID.

Locker tracks email sending process It is used to quarantee not to send the emails twice.

Sender send emails.