会话已失效 -- Alamofire

问：

我使用单例模式进行网络呼叫，但面临一个问题，任何人都可以帮我解决这个问题：会话无效

会话已失效且没有错误，因此它可能被意外取消初始化。请务必在请求期间保留对会话的引用。

我的网络包装器是

public static let shared = NetworkingClient()
    private var requests = [ApiRequest]()
    private var completedRequests = 0
    private var session: Session!
    func InvalidateSession () {
        if #available(iOS 9.0, *) {
            Alamofire.Session.default.session.getAllTasks { (tasks) in
                    tasks.forEach{ $0.cancel() }
                }
            } else {
            Alamofire.Session.default.session.getTasksWithCompletionHandler { (sessionDataTask, uploadData, downloadData) in
                sessionDataTask.forEach { $0.cancel() }
                uploadData.forEach { $0.cancel() }
                downloadData.forEach { $0.cancel() }
            }
        }
    }

这是我的 Api 调用 secanrio 是增加数量然后崩溃 alomofire 我想停止发送请求多个请求 我只想发送请求 api 1 次

func gasEstimation(chain_Id: Int, contractAddress: String, fromAddress: String, toAddress: String, tokenId: String, contractType: String, quantity: String) {
        let apiRequest = [ApiRequest(type: .get, path: "gasEstimation?chainId=\(chain_Id)&contractAddress=\(contractAddress)&from=\(fromAddress.trimmingCharacters(in: .whitespacesAndNewlines))&to=\(toAddress.trimmingCharacters(in: .whitespacesAndNewlines))&type=\(contractType)&quantity=\(quantity)&tokenId=\(tokenId)")]
        NetworkingClient.shared.performRequest(requests: apiRequest) { path, data, error in
            if data != nil {
                let json =  JSON(data!)
                let gasTokenModel = NftTransferModel(json: json)
                self.presenter?.onReceiveFee(estimationFee: gasTokenModel,error: nil)
            }else{
                let error = JSON(error!)
                self.presenter?.onReceiveFee(estimationFee: nil,error: error["message"].stringValue)
            }
        }
    }