score_run.go

func ScoreReview(ctx context.Context, e FirestoreEvent) error {
	review := e.Value.Fields
	reviweScore := score(review.Text.Value)

	ref := client.NewRef("scores").Child(review.Author.Value)
	updateTxn := func(node db.TransactionNode) (interface{}, error) {
		var currentScore int
		if err := node.Unmarshal(&currentScore); err != nil {
			return nil, err
		}
		return currentScore + reviweScore, nil
	}
	return ref.Transaction(ctx, updateTxn)
}