code: func (cli *Client) ContainerExecAttach(ctx context.Context, execID string, config types.ExecStartCheck) (types.HijackedResponse, error) {
  	headers := map[string][]string{"Content-Type": {"application/json"}}
  	return cli.postHijacked(ctx, "/exec/"+execID+"/start", nil, config, headers)
  }
docs: // ContainerExecAttach attaches a connection to an exec process in the server.
  // It returns a types.HijackedConnection with the hijacked connection
  // and the a reader to get output. It's up to the called to close
  // the hijacked connection by calling types.HijackedResponse.Close.