I have two domain names connected to two different servers. a backend server called www.funfun.io,and a fron end server called 'v2.10studio.tech'

I want to proxy a certain route from 'v2.10studio.tech' to the backend server.

in the backend server there are other domain names which makes it necessarily to define the host in the header.

nginx configuration in the backend server.

server {
listen 443 ssl;

server_name funfun.io www.funfun.io;
.....
}

nginx configuration in the frontend server.

server {
listen              443 ssl;
ssl_certificate     /etc/letsencrypt/live/v2.10studio.tech/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/v2.10studio.tech/privkey.pem;
server_name v2.10studio.tech;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_prefer_server_ciphers on;
ssl_session_timeout 1d;
ssl_stapling on;
ssl_stapling_verify on;
add_header Strict-Transport-Security max-age=15768000;
add_header X-Frame-Options "";


location ~ /auth/(.*) {
    proxy_pass https://funfun/10studio/auth/$1?$query_string;
    proxy_set_header Host www.funfun.io;
    proxy_http_version  1.1;
    proxy_cache_bypass  $http_upgrade;

    proxy_set_header Upgrade           $http_upgrade;
    proxy_set_header Connection        "upgrade";
    proxy_set_header X-Real-IP         $remote_addr;
    proxy_set_header X-Forwarded-For   $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_set_header X-Forwarded-Host  $host;
    proxy_set_header X-Forwarded-Port  $server_port;

 }

the logs I'am getting when requesting the route.

2020/04/26 14:56:01 [error] 42#42: *1 SSL_do_handshake() failed (SSL: error:14094410:SSL routines:ssl3_read_bytes:sslv3 alert handshake failure:SSL alert number 40) while SSL handshaking to upstream, client: 193.52.24.26, server: v2.10studio.tech, request: "GET /auth/google HTTP/1.1", upstream: "https://104.27.153.135:443/10studio/auth/google?", host: "v2.10studio.tech"

2020/04/26 14:56:01 [warn] 42#42: *1 upstream server temporarily disabled while SSL handshaking to upstream, client: 193.52.24.26, server: v2.10studio.tech, request: "GET /auth/google HTTP/1.1", upstream: "https://104.27.153.135:443/10studio/auth/google?", host: "v2.10studio.tech"
193.52.24.26 - - [26/Apr/2020:14:56:01 +0000] "GET /auth/google HTTP/1.1" 502 559 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.122 Safari/537.36" "-"