nginx开启websocket代理

• 参考：https://www.nginx.com/blog/websocket-nginx/

• 配置类似下面这样：

location /wsapp/ {
    proxy_pass http://wsbackend;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "Upgrade";
    proxy_set_header Host $host;
}