Online client sample codes failed

🐛 Bug Description

Following https://github.com/microsoft/qlib-server#using-qlib-in-online-mode, the codes failed at
ins = D.list_instruments(D.instrumetns("all"), as_list=True)
with error:
BadNamespaceError Traceback (most recent call last)

To Reproduce

Steps to reproduce the behavior:

1. One key deploy using docker-compose
2. Run the sample codes

~/git/qlib/examples/test.py in 
     81 
     82 qlib.init(**ONLINE_CONFIG)
---> 83 ins = D.list_instruments(D.instruments("all"), as_list=True)
     84 
     85 

~/.local/lib/python3.8/site-packages/qlib/data/data.py in list_instruments(self, instruments, start_time, end_time, freq, as_list)
    948 
    949     def list_instruments(self, instruments, start_time=None, end_time=None, freq="day", as_list=False):
--> 950         return Inst.list_instruments(instruments, start_time, end_time, freq, as_list)
    951 
    952     def features(

~/.local/lib/python3.8/site-packages/qlib/data/data.py in list_instruments(self, instruments, start_time, end_time, freq, as_list)
    808             return instrument
    809 
--> 810         self.conn.send_request(
    811             request_type="instrument",
    812             request_content={

~/.local/lib/python3.8/site-packages/qlib/data/client.py in send_request(self, request_type, request_content, msg_queue, msg_proc_func)
     99         self.sio.on(request_type + "_response", request_callback)
    100         self.logger.debug("try sending")
--> 101         self.sio.emit(request_type + "_request", request_content)
    102         self.sio.wait()

~/.local/lib/python3.8/site-packages/socketio/client.py in emit(self, event, data, namespace, callback)
    326         namespace = namespace or '/'
    327         if namespace not in self.namespaces:
--> 328             raise exceptions.BadNamespaceError(
    329                 namespace + ' is not a connected namespace.')
    330         self.logger.info('Emitting event "%s" [%s]', event, namespace)

BadNamespaceError: / is not a connected namespace.

Expected Behavior

Screenshot

Environment

Note: User could run cd scripts && python collect_info.py all under project directory to get system information
and paste them here directly.

Qlib version: 0.6.1

Python version: ['3.8.5 (default, Jul 28 2020, 12:59:40) ', '[GCC 9.3.0]']

linux_distribution: N/A
system: Linux
machine: x86_64
platform: Linux-4.19.104-microsoft-standard-x86_64-with-glibc2.29
version: #1 SMP Wed Feb 19 06:37:35 UTC 2020

Additional Notes

sockerio version is latest 5.0.4 which is not what qlib recommends. But when I manually installed socketio 3.1.2, it thrown other probem which can't connect server.