code: func (cli *Client) DiskUsage(ctx context.Context) (types.DiskUsage, error) {
  	var du types.DiskUsage
  
  	serverResp, err := cli.get(ctx, "/system/df", nil, nil)
  	defer ensureReaderClosed(serverResp)
  	if err != nil {
  		return du, err
  	}
  
  	if err := json.NewDecoder(serverResp.body).Decode(&du); err != nil {
  		return du, fmt.Errorf("Error retrieving disk usage: %v", err)
  	}
  
  	return du, nil
  }
docs: // DiskUsage requests the current data usage from the daemon