Upgraded from 3.7 to 3.8 broke websockets! help!

Troubleshooting
21

@jasonblais

  1. Mattermost instance just only one domain, but Nginx reverse proxy server has multi domain with virtual host.
  2. "AllowCorsFrom": "" -> websocket does not work (client 403 error), mattermost instance (websocket connect err: websocket: origin not allowed code=500
  1. "AllowCorsFrom": "domain.com" -> same to “”, websocket does not work (client 403 error), mattermost instance (websocket connect err: websocket: origin not allowed code=500

thanks for your help.