code: func extractStorageAccountFromVHDURL(vhdURL string) (string, string) {
  	u, err := url.Parse(vhdURL)
  	if err != nil {
  		log.Warn(fmt.Sprintf("URL parse error: %v", err), logutil.Fields{"url": vhdURL})
  		return "", ""
  	}
  	parts := strings.SplitN(u.Host, ".", 2)
  	if len(parts) != 2 {
  		log.Warnf("Could not split account name and storage base URL: %s", vhdURL)
  		return "", ""
  	}
  	return parts[0], strings.TrimPrefix(parts[1], "blob.") // "blob." prefix will added by azure storage sdk
  }
docs: // extractStorageAccountFromVHDURL parses a blob URL and extracts the Azure
  // Storage account name from the URL, namely first subdomain of the hostname and
  // the Azure Storage service base URL (e.g. core.windows.net). If it could not
  // be parsed, returns empty string.