app.lua

local lapis = require "lapis"
local app = lapis.Application()

app:get("/", function()
	local http = require "lapis.nginx.http"
	local util = require "lapis.util"
	local api = "https://www.googleapis.com/pagespeedonline/v1/runPagespeed?"

	local res, status = http.simple(api .. util.encode_query_string {
		url = "http://leafo.net",
		key = "xxx",
		filter_third_party_resources = "true",
		screenshot = "true",
		strategy = "desktop"
	})

	return res
end)

lapis.serve(app)

nginx.conf

worker_processes ${{NUM_WORKERS}};
error_log stderr notice;
daemon off;

events {
  worker_connections 1024;
}

http {
  include mime.types;

  server {
    listen ${{PORT}};
    lua_code_cache ${{CODE_CACHE}};

    location / {
			set $_url "";
      default_type text/html;
      content_by_lua_file "app.lua";
    }

    location /static/ {
      alias static/;
    }

    location /favicon.ico {
      alias static/favicon.ico;
    }

		location /proxy {
    internal;
    rewrite_by_lua "
      local req = ngx.req

      for k,v in pairs(req.get_headers()) do
        if k ~= 'content-length' then
          req.clear_header(k)
        end
      end

      if ngx.ctx.headers then
        for k,v in pairs(ngx.ctx.headers) do
          req.set_header(k, v)
        end
      end
    ";

    resolver 8.8.8.8;
    proxy_http_version 1.1;
    proxy_pass $_url;
}
  }
}