使用 流式下载大文件时，内存依然不释放，下载超大文件时，直接内存溢出

[topws]

let request = OSSGetObjectRequest()
request.bucketName = unpackedConfig.bucket
request.objectKey = path
request.downloadProgress = downloadProgress

    request.onRecieveData = { data in
        fileHandle?.seekToEndOfFile()
        fileHandle?.write(data)
    }
    
    let getTask = unpackedClient.getObject(request)
    getTask.continue({ task in
        fileHandle?.closeFile()
        
        if let error = task.error {
            completion?(nil, error)
        } else {
            completion?(downloadToFileURL.path, nil)
        }
        return nil
    }, cancellationToken: nil)