This is example for /etc/nginx/sites-available/default file

nginx-default-file-example

upstream puma {
  server unix:///var/www/apps/PROJECT/shared/sockets/puma.sock;
}

server {
  listen 80;
  server_name 'example.com';

  # Discourage deep links by using a permanent redirect to home page of HTTPS site
  #return 301 https://$host;

  # Alternatively, redirect all HTTP links to the matching HTTPS page
  return 301 https://$server_name$request_uri;
}

server {
  server_name 'exampple.com';
  listen 443 ssl;

  root /var/www/apps/PROJECT/shared/public;

  ssl_certificate     /etc/nginx/ssl/exampple.chained.crt;
  ssl_certificate_key /etc/nginx/ssl/exampple.com.key;
  ssl_protocols       TLSv1 TLSv1.1 TLSv1.2;
  ssl_ciphers         HIGH:!aNULL:!MD5;

  add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; always";

  ssl_stapling on;
  ssl_stapling_verify on;
  ssl_trusted_certificate /etc/nginx/ssl/exampple.com.chained.crt;

  access_log /var/www/apps/PROJECT/shared/log/puma.stdout.log;
  error_log /var/www/apps/PROJECT/shared/log/puma.stderr.log info;

  location ^~ /assets/ {
    gzip_static on;
    expires max;
    add_header Cache-Control public;
  }

  try_files $uri/index.html $uri @puma;
  location @puma {
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_redirect off;

    proxy_pass http://puma;
  }

  error_page 500 502 503 504 /500.html;
  client_max_body_size 10M;
  keepalive_timeout 10;
}