code: func getUser(ctx context.Context, client *http.Client) (*drive.User, error) {
  	srv, err := drive.New(client)
  	if err != nil {
  		return nil, err
  	}
  	about, err := srv.About.Get().
  		Context(ctx).
  		Fields("user(displayName,emailAddress,permissionId)").Do()
  	if err != nil {
  		return nil, err
  	}
  	return about.User, nil
  }
docs: // getUser returns the authenticated Google Drive user's User value,
  // containing their name, email address, and "permission ID",
  // which is the "The user's ID as visible in Permission resources" according
  // to https://developers.google.com/drive/v3/reference/about#resource
  // The permission ID becomes the "userID" (AcctAttrUserID) value on the
  // account's "importerAccount" permanode.