code: func (service *GCSService) GetObjectSize(ctx context.Context, params GCSObjectParams) (int64, error) {
  	attrs, err := service.GetObjectAttrs(ctx, params)
  	if err != nil {
  		return 0, err
  	}
  
  	return attrs.Size, nil
  }
docs: // GetObjectSize returns the byte length of the specified GCS object.