code: func IsSuccessful(ctx context.Context, client client.APIClient, containerID string) func(log poll.LogT) poll.Result {
  	return func(log poll.LogT) poll.Result {
  		inspect, err := client.ContainerInspect(ctx, containerID)
  		if err != nil {
  			return poll.Error(err)
  		}
  		if inspect.State.Status == "exited" {
  			if inspect.State.ExitCode == 0 {
  				return poll.Success()
  			}
  			return poll.Error(errors.Errorf("expected exit code 0, got %d", inspect.State.ExitCode))
  		}
  		return poll.Continue("waiting for container to be \"exited\", currently %s", inspect.State.Status)
  	}
  }
docs: // IsSuccessful verifies state.Status == "exited" && state.ExitCode == 0