code: func (s *serviceCache) GetByKey(key string) (interface{}, bool, error) {
  	s.mu.Lock()
  	defer s.mu.Unlock()
  	if v, ok := s.serviceMap[key]; ok {
  		return v, true, nil
  	}
  	return nil, false, nil
  }
docs: // GetByKey returns the value stored in the serviceMap under the given key