code: func (e *eventLogger) lastEventObservationFromCache(key string) eventLog {
  	value, ok := e.cache.Get(key)
  	if ok {
  		observationValue, ok := value.(eventLog)
  		if ok {
  			return observationValue
  		}
  	}
  	return eventLog{}
  }
docs: // lastEventObservationFromCache returns the event from the cache, reads must be protected via external lock