code: func (m *GormCommentRepository) CheckExists(ctx context.Context, id uuid.UUID) error {
  	defer goa.MeasureSince([]string{"goa", "db", "comment", "exists"}, time.Now())
  	return repository.CheckExists(ctx, m.db, Comment{}.TableName(), id)
  }
docs: // CheckExists returns nil if the given ID exists otherwise returns an error