for i := 0; i < 100; i++ {
		wg.Add(1)
		go func() {
			user := User{Name: "jinzhu"}
			tx.Create(&user)

			var result User
			tx.First(&result)
			wg.Done()
		}()
	}
	wg.Wait()

	conn, ok := tx.ConnPool.(*gorm.PreparedStmtDB)
	AssertEqual(t, ok, true)
	AssertEqual(t, len(conn.Stmts), 2)
	for _, stmt := range conn.Stmts {
		if stmt == nil {
			t.Fatalf("stmt cannot bee nil")
		}

		db.Mux.RUnlock()
		// wait for other goroutines prepared
		<-stmt.prepared
		if stmt.prepareErr != nil {
			return Stmt{}, stmt.prepareErr
		}

		return *stmt, nil
	}
	db.Mux.RUnlock()

	db.Mux.Lock()
	// double check
	if stmt, ok := db.Stmts[query]; ok && (!stmt.Transaction || isTransaction) {
		db.Mux.Unlock()
		// wait for other goroutines prepared
		<-stmt.prepared