在异步调用中从URLSession快速返回数据

Question

无法从我的HTTPrequest返回数据，并且我也无法使完成处理程序正常工作。因此，请协助我解决这个问题：

static func Login(urlExtension: String, userName: String, userPassword: String) -> String
    {

        let url = baseUrl?.appendingPathComponent(urlExtension)
        var request = URLRequest(url: url!)

        request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
        request.setValue("application/json", forHTTPHeaderField: "Accept")
        request.httpMethod = "POST"
        let dataOpt = "Username=\(userName)&Password=\(userPassword)&grant_type=password"
        request.httpBody = dataOpt.data(using: String.Encoding.ascii, allowLossyConversion: false)
        let task = URLSession.shared.dataTask(with: request){
            (data: Data?, response: URLResponse?, error: Error?) in

            if error != nil
            {
                return
            }
            //Let's convert response sent from server side code to a NSDictionary object:
            do{
                let json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? NSDictionary
                print(json)
                if let parseJSON = json {

                    let accessToken = parseJSON["access_token"] as? String
                    let userName = parseJSON["userName"] as? String

                    let saveAccessToken: Bool = KeychainWrapper.standard.set(accessToken!, forKey: "accessToken")
                    let saveUserName: Bool = KeychainWrapper.standard.set(userName!, forKey: "userName")


                }
                else{

                }
            }catch{
            }
        }
        return "test"
    }

这是被调用的方法，我无法从URLSession.shared.data内部的响应中返回解析的访问令牌，

我尝试实现完成处理程序，但是我不知道实现它是否出错，还是无法在模拟器中正确测试

此方法在视图控制器之外的API管理器中实现，并且baseURL var是全局变量