Workaround for http://openradar.me/radar?id=5847108682776576

gistfile1.m

- (void)cancelLongRunningTasks:(id)sender {
    NSDate *date = [NSDate date];
    
    void (^CompletionHandler)(NSArray *dataTasks, NSArray *uploadTasks, NSArray *downloadTasks) = ^(NSArray *dataTasks, NSArray *uploadTasks, NSArray *downloadTasks) {
        for (NSURLSessionDownloadTask *task in downloadTasks) {
            if (task.state == NSURLSessionTaskStateRunning) {
                NSDate *startDate = self.sessionDownloadTaskStartDates[@(task.taskIdentifier)];
                if (startDate) {
                    NSTimeInterval interval = [date timeIntervalSinceDate:startDate];
                    if (interval > 30) {
                        [task cancel];
                    }
                }
            }
        }
    };
    
    [self.session getTasksWithCompletionHandler:CompletionHandler];
}