How to custom stun server

With the default config, it kept telling me : [FATAL] [janus.c:main:3554] Invalid STUN address stun.l.google.com:19302

The whole log is below

docker run --rm --name mattermost-webrtc -p 7088:7088 -p 7089:7089 -p 8188:8188 -p 8189:8189 mattermost/webrtc:latest
---------------------------------------------------
  Starting Meetecho Janus (WebRTC Gateway) v0.2.2
---------------------------------------------------

Checking command line arguments...
Debug/log level is 4
Debug/log timestamps are disabled
Debug/log colors are enabled
Adding 'vmnet' to the ICE ignore list...
Using 172.17.0.2 as local IP...
Token based authentication enabled
Initializing ICE stuff (Full mode, ICE-TCP candidates disabled, IPv6 support disabled)
STUN server to use: stun.l.google.com:19302
ICE handles watchdog started
Testing STUN server: message is of 20 bytes
[FATAL] [ice.c:janus_ice_set_stun_server:770] No response to our STUN BINDING test
[FATAL] [janus.c:main:3554] Invalid STUN address stun.l.google.com:19302

And are there any STUN server avaliable from China since there is a Great Wall...

mattermost / mattermost-webrtc

How to custom stun server #4