feat(docs): how-to use transactions with pgx

[pedro-tiple]

Update the documentation as described in issue #3192.

[fr11nik]

I prefer to create into db package ReadCommited function that start transaction

// any sqlc function type Handler func(*Queries) error func (store *SQLStore) ReadCommited(ctx context.Context, fn Handler) error{tx, err := store.db.Begin(ctx) if err != nil{return err } defer func(){rbErr := tx.Rollback(ctx) if rbErr != nil{// Log the rollback error log.Printf("rollback error: %v", rbErr) } }() err = fn(store.WithTx(tx)) if err != nil{// Return the original error along with the rollback error if any return fmt.Errorf("transaction error: %v", err) } return tx.Commit(ctx) } 

And use into store.go

type Store interface{Querier ReadCommited(ctx context.Context, fn Handler) error } 

Use it via

func bumpCounter(ctx context.Context,store tutorial.Store, id int32) error{err := store.ReadCommited(ctx,func(qtx *tutorial.Queries) error{r, err := qtx.GetRecord(ctx, id) if err != nil{return err } return qtx.UpdateRecord(ctx,tutorial.UpdateRecordParams{ID: r.ID, Counter: r.Counter + 1, }) }) return err }