code: func (d *stiDocker) DownloadFromContainer(containerPath string, w io.Writer, container string) error {
  	ctx, cancel := getDefaultContext()
  	defer cancel()
  	readCloser, _, err := d.client.CopyFromContainer(ctx, container, containerPath)
  	if err != nil {
  		return err
  	}
  	defer readCloser.Close()
  	_, err = io.Copy(w, readCloser)
  	return err
  }
docs: // DownloadFromContainer downloads file (or directory) from the container.