Dynamic Nginx upstream nodes using Consul

consul.lua

module("resty.consul", package.seeall)

_VERSION = '0.1.0'

function service_nodes(service)
  local http = require "resty.http"
  local json = require "cjson"
  local hc = http:new()

  local upstream = ""
  
  local ok, code, headers, status, body = hc:request {
      url = "http://127.0.0.1:8500/v1/catalog/service/" .. service,
      port = 8500,
      method = "GET"
  }
  
  if body then
    local nodes = json.decode(body)
    node = math.random(1, #nodes)
    upstream = nodes[node]["Address"] .. ":" .. nodes[node]["ServicePort"]    
  end
  
  return upstream
end            

nginx.conf

worker_processes  1;

events {
    worker_connections  1024;
}

http {
    include       mime.types;
    default_type  application/octet-stream;
    lua_package_path "/etc/nginx/lua/?.lua;;";
    lua_code_cache off;
    init_by_lua 'consul = require "resty.consul"';

    sendfile        on;
    keepalive_timeout  65;

    server {
        listen       80;
        server_name  localhost;
        location / {
            set $upstream "";
            rewrite_by_lua 'ngx.var.upstream = consul.service_nodes("www")';
            proxy_buffering             off;
            proxy_set_header            Host $host;
            proxy_set_header            X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_redirect              off;
            proxy_connect_timeout       10;
            proxy_send_timeout          30;
            proxy_read_timeout          30;
            proxy_pass                  http://$upstream;          
        }
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }
    }
}

I want to use this or something similar with Docker Swarm. Is Lua the only programming language that can be used? Also what are the installation instructions for the different lua modules?