Python中使用async/await下载文件失败，如何解决？

目前需要从一个 FTP 服务器下载 3 万多个小文件，之前用 multiprocessing 总是下一部分之后就停了，所以尝试用异步加快下载：

class pdb:
    def __init__(self):
        self.ids = []
        self.dl_id = []
        self.err_id = []
async def download_file(self, session, url):
    try:
        with async_timeout.timeout(10):
            async with session.get(url) as remotefile:
                if remotefile.status == 200:
                    data = await remotefile.read()
                    return {"error": "", "data": data}
                else:
                    return {"error": remotefile.status, "data": ""}
    except Exception as e:
        return {"error": e, "data": ""}

async def unzip(self, session, work_queue):
    while not work_queue.empty():
        queue_url = await work_queue.get()
        print(queue_url)
        data = await self.download_file(session, queue_url)
        id = queue_url[-11:-7]
        ID = id.upper()
        if not data["error"]:
            saved_pdb = os.path.join("./pdb", ID, f'{ID}.pdb')
            if ID not in self.dl_id:
                self.dl_id.append(ID)
            with open(f"{id}.ent.gz", 'wb') as f:
                f.write(data["data"].read())
            with gzip.open(f"{id}.ent.gz", "rb") as inFile, open(saved_pdb, "wb") as outFile:
                shutil.copyfileobj(inFile, outFile)
            os.remove(f"{id}.ent.gz")
        else:
            self.err_id.append(ID)

def download_queue(self, urls):
    loop = asyncio.get_event_loop()
    q = asyncio.Queue(loop=loop)
    [q.put_nowait(url) for url in urls]
    con = aiohttp.TCPConnector(limit=10)
    with aiohttp.ClientSession(loop=loop, connector=con) as session:
        tasks = [asyncio.ensure_future(self.unzip(session, q)) for _ in range(len(urls))]
        loop.run_until_complete(asyncio.gather(*tasks))
    loop.close()
if name == “main”:
x = pdb()
urls = [‘ftp://ftp.wwpdb.org/pub/pdb/data/structures/divided/pdb/nf/pdb4nfn.ent.gz’, ‘ftp://ftp.wwpdb.org/pub/pdb/data/structures/divided/pdb/ny/pdb4nyj.ent.gz’, ‘ftp://ftp.wwpdb.org/pub/pdb/data/structures/divided/pdb/mn/pdb2mnz.ent.gz’, ‘ftp://ftp.wwpdb.org/pub/pdb/data/structures/divided/pdb/ra/pdb4ra4.ent.gz’, ‘ftp://ftp.wwpdb.org/pub/pdb/data/structures/divided/pdb/x5/pdb4x5w.ent.gz’, ‘ftp://ftp.wwpdb.org/pub/pdb/data/structures/divided/pdb/dm/pdb2dmq.ent.gz’, ‘ftp://ftp.wwpdb.org/pub/pdb/data/structures/divided/pdb/n7/pdb2n7r.ent.gz’, ‘ftp://ftp.wwpdb.org/pub/pdb/data/structures/divided/pdb/om/pdb2omv.ent.gz’, ‘ftp://ftp.wwpdb.org/pub/pdb/data/structures/divided/pdb/oy/pdb3oy8.ent.gz’, ‘ftp://ftp.wwpdb.org/pub/pdb/data/structures/divided/pdb/fe/pdb3fej.ent.gz’, ‘ftp://ftp.wwpdb.org/pub/pdb/data/structures/divided/pdb/hw/pdb2hw9.ent.gz’]
x.download_queue(urls)

报错信息如下：

Traceback (most recent call last):
File "test.py", line 111, in <module>
x.download_queue(urls)
File "test.py", line 99, in download_queue
loop.run_until_complete(asyncio.gather(*tasks))
File "/home/yz/miniconda3/lib/python3.6/asyncio/base_events.py", line 467, in run_until_complete
return future.result()
File "test.py", line 73, in unzip
data = await self.download_file(session, queue_url)
File "test.py", line 65, in download_file
return {"error": remotefile.status, "data": ""}
File "/home/yz/miniconda3/lib/python3.6/site-packages/async_timeout/init.py", line 46, in exit
raise asyncio.TimeoutError from None
concurrent.futures._base.TimeoutError

请大家帮忙看看。谢谢！