code: func (s *Subscriber) Subscribe(e Event, f interface{}) *Subscriber {
  	unsubscribe := s.events.subscribe(e, f)
  	s.unsuscribes = append(s.unsuscribes, unsubscribe)
  	return s
  }
docs: // Subscribe subscribes a function to the given event. Emit fails if the
  // subscribed func have more arguments than the emitted event.
  //
  // Panics if f is not a func.