code: func (e *Engine) ExecExitCode(ctx context.Context, execID string) (int, error) {
  	r, err := e.client.ContainerExecInspect(ctx, execID)
  	if err != nil {
  		return -1, err
  	}
  	return r.ExitCode, nil
  }
docs: // ExecExitCode get exec return code