             return r
         }
         set {
-            taskAttributesIsolation.async { self._priority = newValue }
+            taskAttributesIsolation.async(flags: .barrier) { self._priority = newValue }
         }
     }
     fileprivate var _priority: Float = URLSessionTaskPriorityDefault

            taskAttributesIsolation.sync { r = self._countOfBytesSent }
            return r
        }
        set { taskAttributesIsolation.async { self._countOfBytesSent = newValue } }
    }

    fileprivate var _countOfBytesSent: Int64 = 0

            taskAttributesIsolation.sync { r = self._response }
            return r
        }
        set { taskAttributesIsolation.async(flags: .barrier) { self._response = newValue } }
    }
    fileprivate var _response: URLResponse? = nil
    
