code: func getResourceGroupFromDiskURI(diskURI string) (string, error) {
  	fields := strings.Split(diskURI, "/")
  	if len(fields) != 9 || fields[3] != "resourceGroups" {
  		return "", fmt.Errorf("invalid disk URI: %s", diskURI)
  	}
  	return fields[4], nil
  }
docs: // get resource group name from a managed disk URI, e.g. return {group-name} according to
  // /subscriptions/{sub-id}/resourcegroups/{group-name}/providers/microsoft.compute/disks/{disk-id}
  // according to https://docs.microsoft.com/en-us/rest/api/compute/disks/get