Nginx docker proxy container not redirecting?

I'm attempting to bake the following Nginx reverse proxy configuration into a docker image:

    server {
        listen 80;
        server_name 203.0.113.2;

        proxy_set_header X-Real-IP  $remote_addr; # pass on real client IP

        location / {
            proxy_pass http://203.0.113.1:3000;
        }
    }

I'm currently just putting that into a volume and mapping it like this:

-v nginx-data:/etc/nginx/conf.d/

That works and it when started the container performs as a reverse proxy, but when I bake it in like this:

Dockerfile

  FROM nginx
  COPY gogs.conf /etc/nginx/conf.d/gogs.conf

Start the container from the image like this:

docker run --name gogs-nginx-container -d gogs-nginx

And finally visit it at its assigned IP address http://172.17.0.3/ I just get the "Welcome to Nginx" page, instead of seeing and it does not redirect to 203.0.113.1:3000.

Any ideas on how to troubleshoot this?