I'm trying to use a dockerized version of nginx as a proxy server for my node (ExpressJS) application. Without any configuration to nginx and publishing port 80 for the container, I am able to see the default nginx landing page. So I know that much is working.

Now I can mount my sites-enabled directory that contains the configuration for `proxy_pass localhost:3000`. I have my node application running locally (not in any Docker container) and I can access it via port 3000 (i.e. `localhost:3000`). However, I would assume that with nginx container running, mapped to port 80, and proxying my localhost:3000, that I would be able to see my *very* simple (hello world) application. Instead I receive a 502. 

Do I need to pass something into docker? Is this likely a nginx configuration error? Here is my nginx configuration:

```
server {
  listen 0.0.0.0:80;
  server_name localhost;

  location / {
    proxy_pass http://localhost:3000;
  }
}

```

I have tried using [this question](https://stackoverflow.com/questions/24319662/from-inside-of-a-docker-container-how-do-i-connect-to-the-localhost-of-the-mach?rq=1) but it did not seem to help. That is unless I'm doing something completely wrong.