     }
     
     public func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data){
-        self.data? += data
+        self.data += data
     }
 }
  

    var credential: URLCredential?
    var completionHandler: ((Data?, URLResponse?, NSError?) -> Swift.Void)?
    var response:URLResponse?
    var data:Data?
    var dataTask: URLSessionDataTask?
    var error: NSError?
    

    public func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive response: URLResponse, completionHandler: (URLSession.ResponseDisposition) -> Swift.Void){
        self.dataTask = dataTask
        self.response = response
        completionHandler(URLSession.ResponseDisposition.allow)

        
    }
    
