code: func getJob(c context.Context, id JobID) (*Job, error) {
  	job := &Job{ID: id}
  	switch err := datastore.Get(c, job); {
  	case err == datastore.ErrNoSuchEntity:
  		return nil, ErrNoSuchJob
  	case err != nil:
  		return nil, errors.Annotate(err, "transient datastore error").Tag(transient.Tag).Err()
  	default:
  		return job, nil
  	}
  }
docs: // getJob fetches a Job entity.
  //
  // Recognizes and tags transient errors.