Error 200 during WebSocket handshake: Aws load balancer + ec2 websocket

Question

I'm using load balancer in front of an aws ec2 instance(I will have more in future). In this ec2, I have a website being served by nginx on port 80, a nodejs app listening on 8080 and the websocket on 4555.

My nginx.conf has rules to pass the requests based on location / as you can see:

server {
        listen       80 default_server;
        listen       [::]:80 default_server;
        server_name  localhost;
        root         /var/www/html;

        # Load configuration files for the default server block.
        include /etc/nginx/default.d/*.conf;

       #try_files $uri $uri/ @rewrite;
       # location @rewrite {
       #    rewrite ^/(.*)$ /index.php?param=$1;
       #}

    location /api {
               proxy_pass http://127.0.0.1:8080;
               proxy_http_version 1.1;
               proxy_set_header Upgrade $http_upgrade;
               proxy_set_header Connection 'upgrade';
               proxy_set_header Host $host;
               proxy_cache_bypass $http_upgrade;
        }

    location /chat {
                proxy_pass http://127.0.0.1:4555;
                proxy_http_version 1.1;
                proxy_set_header Upgrade $http_upgrade;
                proxy_set_header Connection 'upgrade';
                proxy_set_header Host $host;
                proxy_cache_bypass $http_upgrade;
        }
}

It was working when I was redirectioning the connection directly to the instance but now that we have the loadbalancer in the front it doesn't work anymore.

web application output:

WebSocket connection to 'wss://www.domain.com/socket.io/?EIO=3&transport=websocket' failed: Error during WebSocket handshake: Unexpected response code: 200

And this is the headers:

Request URL: wss://www.domain.com/socket.io/?EIO=3&transport=websocket
Request Method: GET
Status Code: 200 OK
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Connection: keep-alive
Content-Type: text/html; charset=UTF-8
Date: Mon, 20 May 2019 18:53:37 GMT
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Pragma: no-cache
Server: nginx/1.14.1
Transfer-Encoding: chunked
X-Powered-By: PHP/5.6.40
Accept-Encoding: gzip, deflate, br
Accept-Language: pt-BR,pt;q=0.9,en-US;q=0.8,en;q=0.7
Cache-Control: no-cache
Connection: Upgrade
Cookie: PHPSESSID=a6v5ebp25cajb1dj9s6je605a3
Host: www.domain.com
Origin: https://www. domain.com
Pragma: no-cache
Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits
Sec-WebSocket-Key: kmYaufsBu3UFD+qGm1vlGA==
Sec-WebSocket-Version: 13
Upgrade: websocket
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.157 Safari/537.36
EIO: 3
transport: websocket