code: func (d *kubeDockerClient) CreateExec(id string, opts dockertypes.ExecConfig) (*dockertypes.IDResponse, error) {
  	ctx, cancel := d.getTimeoutContext()
  	defer cancel()
  	resp, err := d.client.ContainerExecCreate(ctx, id, opts)
  	if ctxErr := contextError(ctx); ctxErr != nil {
  		return nil, ctxErr
  	}
  	if err != nil {
  		return nil, err
  	}
  	return &resp, nil
  }
docs: // TODO(random-liu): Add unit test for exec and attach functions, just like what go-dockerclient did.