You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: db_with_pool.go
    path of file: ./repos/river/internal/testdb
    
    the code of the file until where you have to start completion: package testdb

import (
	"context"
	"log/slog"
	"sync"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"
	"github.com/jackc/puddle/v2"
)

// DBWithPool is a wrapper for a puddle resource for a test database. The
// database is made available via a preconfigured pgxpool.Pool.
type DBWithPool struct {
	res     *puddle.Resource[*poolWithDBName]
	manager *Manager
	dbName  string
	logger  *slog.Logger

	closeOnce sync.Once
}

// Release releases the DBWithPool back to the Manager. This should be called
// when the test is finished with the database.

    
func (db *DBWithPool) release() {
	// Close and recreate the connection pool for 2 reasons:
	// 1. ensure tests don't hold on to connections
	// 2. If a test happens to close the pool as a matter of course (i.e. as part of a defer)
	//    then we don't reuse a closed pool.
	db.res.Value().pool.Close()

	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	newPgxPool, err := pgxpool.NewWithConfig(ctx, db.res.Value().config)
	if err != nil {
		db.res.Destroy()
		return
	}
	db.res.Value().pool = newPgxPool

	if db.manager.cleanup != nil {
		if err := db.manager.cleanup(ctx, newPgxPool); err != nil {
			db.logger.Error("testdb.DBWithPool: Error during release cleanup", "err", err)
			db.res.Destroy()
			return
		}
	}

	// Finally this resource is ready to be reused:
	db.res.Release()
}