Fix race condition in pgxstore cleanup

- Run this test with the race detector on

pgxstore/pgxstore.go

@@ -28,6 +28,7 @@ func New(pool *pgxpool.Pool) *PostgresStore {
 func NewWithCleanupInterval(pool *pgxpool.Pool, cleanupInterval time.Duration) *PostgresStore {
 	p := &PostgresStore{pool: pool}
 	if cleanupInterval > 0 {
+		p.stopCleanup = make(chan bool)
 		go p.startCleanup(cleanupInterval)
 	}
 	return p
@@ -99,7 +100,6 @@ func (p *PostgresStore) All() (map[string][]byte, error) {
 }
 
 func (p *PostgresStore) startCleanup(interval time.Duration) {
-	p.stopCleanup = make(chan bool)
 	ticker := time.NewTicker(interval)
 	for {
 		select {

pgxstore/pgxstore_test.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"os"
 	"reflect"
+	"strconv"
 	"testing"
 	"time"
 
@@ -241,6 +242,26 @@ func TestCleanup(t *testing.T) {
 	}
 }
 
+func TestStopCleanup(t *testing.T) {
+	ctx := context.Background()
+
+	dsn := os.Getenv("SCS_POSTGRES_TEST_DSN")
+	pool, err := pgxpool.New(ctx, dsn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer pool.Close()
+
+	for i := 0; i < 100; i++ {
+		t.Run(strconv.Itoa(i), func(t *testing.T) {
+			t.Parallel()
+			p := New(pool)
+			time.Sleep(100 * time.Millisecond)
+			defer p.StopCleanup()
+		})
+	}
+}
+
 func TestStopNilCleanup(t *testing.T) {
 	dsn := os.Getenv("SCS_POSTGRES_TEST_DSN")
 	pool, err := pgxpool.New(context.Background(), dsn)