code: func (ctl *Controller) tq() *tq.Dispatcher {
  	ctl.m.RLock()
  	defer ctl.m.RUnlock()
  	if ctl.disp == nil {
  		panic("mapper.Controller wasn't installed into tq.Dispatcher yet")
  	}
  	return ctl.disp
  }
docs: // tq returns a dispatcher set in Install or panics if not set yet.
  //
  // Grabs the reader lock inside.