struct Bank {
    private var customer: BankItemQueue<Customer>
    private let bankmanager: BankManager
    
init(customer: BankItemQueue<Customer>, bankmanager: BankManager) {
        self.customer = customer
        self.bankmanager = bankmanager
    }
}

Thread.sleep(forTimeInterval: customer.bankingType.bankingProcessingTime)

 private let depositSemaphore = DispatchSemaphore(value: NumberOfBankManager.deposit.rawValue)
    private let loanSemaphore = DispatchSemaphore(value: NumberOfBankManager.loan.rawValue)

private func giveTask(for customerList: BankItemQueue<Customer>) {
        var customerList = customerList
        while let completeCustomer = customerList.deQueue() {
            DispatchQueue.global().async(group: bankingGroup) {
                switch completeCustomer.bankingType {
                case .deposit:
                    self.depositSemaphore.wait()
                    self.bankmanager.handleBanking(for: completeCustomer)
                    self.depositSemaphore.signal()
                case .loan:
                    self.loanSemaphore.wait()
                    self.bankmanager.handleBanking(for: completeCustomer)
                    self.loanSemaphore.signal()
                }
            }
        }
    }