code: func (m TaskManager) HandleTimer(c context.Context, ctl task.Controller, name string, payload []byte) error {
  	if name == statusCheckTimerName {
  		ctl.DebugLog("Timer tick, asking Buildbucket for the build status")
  		if err := m.checkBuildStatus(c, ctl); err != nil {
  			// This is either a fatal or transient error. If it is fatal, no need to
  			// schedule the timer anymore. If it is transient, HandleTimer call itself
  			// will be retried and the timer will be rescheduled then.
  			return err
  		}
  		m.checkBuildStatusLater(c, ctl) // reschedule this check
  	}
  	return nil
  }
docs: // HandleTimer is part of Manager interface.