AFNetworking3.0 如何取消单个网络请求

NSURL *URL = [NSURL URLWithString:@http];

    AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];

    NSURLSessionDataTask *task = [manager GET:URL.absoluteString parameters:nil progress:nil success:^(NSURLSessionTask *task, id responseObject) {

        NSLog(@"JSON: %@", responseObject);

    } failure:^(NSURLSessionTask *operation, NSError *error) {

        NSLog(@"Error: %@", error);

    }];

//取消单个请求

    [task cancel];

//取消当前所有

    [manager.operationQueue cancelAllOperations];