code: func GetAPIKey() (string, error) {
  	mu.RLock()
  	key := apiKey
  	mu.RUnlock()
  	if apiKey != "" {
  		return key, nil
  	}
  	mu.Lock()
  	defer mu.Unlock()
  
  	dir, err := osutil.PerkeepConfigDir()
  	if err != nil {
  		return "", err
  	}
  	slurp, err := wkfs.ReadFile(filepath.Join(dir, apiKeyName))
  	if os.IsNotExist(err) {
  		return "", ErrNoGoogleKey
  	}
  	if err != nil {
  		return "", err
  	}
  	key = strings.TrimSpace(string(slurp))
  	if key == "" {
  		return "", ErrNoGoogleKey
  	}
  	apiKey = key
  	return key, nil
  }
docs: // GetAPIKey returns the Google geocoding API key stored in the Perkeep
  // configuration directory as google-geocode.key.