Bad Gateway error on one Docker container under NGINX

I'm newbie about NGINX, I'm trying to put two services inside the same Docker Container. Every services has his domain.

I found this answer that solve my problem but there is another problem that I'm not be able to solve.

If I use the default.conf below, both services works fine:

server {
    listen 80;
    listen [::]:80;
    #server_name  domain.me www.domain.me;
    server_name  127.0.0.1; # FOR STAGING ONLY

    error_log  /var/log/nginx/error.log warn;
    access_log /var/log/nginx/access.log combined;

    location / {
        proxy_pass http://website:8301; # The port must be the same of PROJECT_PORT
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
        proxy_redirect off;
        # max uploadable file size
        client_max_body_size 4G;
    }

    location /static/ {
        # static folder on the server
        alias /app/web/static-folder/;
    }

    location /media/ {
        # media folder on the server
        alias /app/web/media-folder/;
    }
}

server {
    #server_name  geoserver.domain.me www.geoserver.domain.me;
    server_name 127.0.0.2; # FOR STAGING ONLY

    listen 80;
    listen [::]:80;

    server_tokens off;

    root /usr/share/nginx/html;
    index index.html;

    gzip on;
    gzip_disable "msie6";

    gzip_vary on;
    gzip_proxied any;
    gzip_comp_level 6;
    gzip_buffers 16 8k;
    gzip_http_version 1.1;
    gzip_types
        text/plain
        text/css
        application/json
        application/javascript
        application/x-javascript
        text/xml application/xm
        application/xml+rss
        text/javascript;

    underscores_in_headers on;
    proxy_set_header HOST $host;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_set_header X-Forwarded-Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_buffering on;
    proxy_buffer_size 1k;
    proxy_buffers 24 4k;
    proxy_busy_buffers_size 8k;
    proxy_max_temp_file_size 2048m;
    proxy_temp_file_write_size 32k;

    location / {
            deny all;
            return 301 /geoserver;
    }

    location /geoserver {
        proxy_pass         http://geoserver:8080/geoserver;
    }
}

Instead, if I use the code below, domain1 works but domain2 give 500 Bad Gateway:

upstream domain1 {
    server website:8301; # same container's name of docker-compose.yml
    # NB: The port must be the same of PROJECT_PORT
}

upstream domain2 {
    server geoserver:80; # same container's name of docker-compose.yml
}

server {
    listen 80;
    listen [::]:80;
    server_name  127.0.0.1; # FOR STAGING ONLY

    error_log  /var/log/nginx/error.log warn;
    access_log /var/log/nginx/access.log combined;

    location / {
        proxy_pass http://domain1/;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
        proxy_redirect off;
        # max uploadable file size
        client_max_body_size 4G;
    }

    location /static/ {
        # static folder on the server
        alias /app/web/static-folder/;
    }

    location /media/ {
        # media folder on the server
        alias /app/web/media-folder/;
    }
}

server {
    server_name 127.0.0.2; # FOR STAGING ONLY

    listen 80;
    listen [::]:80;

    server_tokens off;

    root /usr/share/nginx/html;
    index index.html;

    gzip on;
    gzip_disable "msie6";

    gzip_vary on;
    gzip_proxied any;
    gzip_comp_level 6;
    gzip_buffers 16 8k;
    gzip_http_version 1.1;
    gzip_types
        text/plain
        text/css
        application/json
        application/javascript
        application/x-javascript
        text/xml application/xm
        application/xml+rss
        text/javascript;

    underscores_in_headers on;
    proxy_set_header HOST $host;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_set_header X-Forwarded-Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_buffering on;
    proxy_buffer_size 1k;
    proxy_buffers 24 4k;
    proxy_busy_buffers_size 8k;
    proxy_max_temp_file_size 2048m;
    proxy_temp_file_write_size 32k;

    location / {
            deny all;
            return 301 /geoserver;
    }

    location /geoserver {
        proxy_pass         http://domain2/geoserver/;
    }
}

Why happen this?