let serialQueue = DispatchQueue(label: "queue", qos: .utility)

        tableView.selectedRowIndexes.forEach { row in

            serialQueue.async {

                InitData.fetch("someUrl") { initData in
                    let fileManager = FileManager()

                    do {
                        try fileManager.copyItem(atPath: "pathA", toPath: "pathB")
                    }
                    catch let error {
                        print(error)
                    }
                }
            }
        }

tableView.selectedRowIndexes.forEach { row in

        serialQueue.async {

            InitData.fetch("someUrl") { initData in
                let fileManager = FileManager()
                let workItem = DispatchWorkItem {

                    do {
                        try fileManager.copyItem(atPath: "pathA", toPath: "pathB")
                    }
                    catch let error {
                        print(error)
                    }
                }
                DispatchQueue.global(qos: .background).async(execute: workItem)
            }
        }
    }