code: func NewInMemoryUsageStore() (UsageStore, error) {
  	m := &memoryStore{}
  	m.set = make(map[string]memEntry)
  	m.quit = make(chan struct{})
  	go m.garbageCollector()
  	return m, nil
  }
docs: // NewInMemoryUsageStore creates a usage store backed by memory. This usage
  // store is only appropriate for single instance gatekeeper deployments
  // and should not be used for high availablility deployments.