Gorm Transaction Error error = transaction has already been committed or rolled back

I'm aiming to do transaction management in the code below. If there is an error in one of the strategies, I am trying to rollback. While testing the code, I noticed that if the rollback or commit command works once, it gives error = transaction has already been committed or rolled back the second time. How can I resolve this error?

func (d *DistributeService) Distribute(vehicleNumberPlate string, request model.DistributeRequest) (*model.DistributeResponse, error) {
	var response model.DistributeResponse
	response.Vehicle = vehicleNumberPlate
	var routeList []model.RouteResponse
	tx := d.repo.BeginTransaction()
	for _, routes := range request.RouteRequest {
		var routeResponse model.RouteResponse
		strategy, isStrategyExists := d.strategies[routes.DeliveryPoint]
		if isStrategyExists {
			resp, err := strategy.Distribute(routes.Deliveries, vehicleNumberPlate, tx)
			if err != nil {
				tx.Rollback()
				logrus.Errorf("Error while distributing: %v", err)
				return nil, err
			}
			routeResponse.DeliveryPoint = routes.DeliveryPoint
			routeResponse.Deliveries = *resp
			routeList = append(routeList, routeResponse)
		} else {
			logrus.Errorf("Invalid delivery point: %v", routes.DeliveryPoint)
			return nil, errors.New("invalid delivery point")
		}
	}
	response.RouteResponse = routeList
	err := d.checkSackPackagesAreUnloaded()
	tx.Commit()
	if err != nil {
		return nil, err
	}
	return &response, nil
}

You're probably using the same transaction object in each call.
If it was closed once - for whatever reason - you need to create a new transaction object.

Why do I say you are probably using the same transaction object you ask?
Because you're basically passing a pointer to d *DistributeService.
And then use tx := d.repo.BeginTransaction(). We can't tell what that code does, but I'm pretty sure you're returning the same transaction object here for subsequent runs.

The solution is to create a new transaction object every time this method is called, f.e. with tx := db.Begin() as described in the docs.