My backend container is nginx that redirects http on port 80 to https on port 443. It uses a self-signed certificate.
When I try to run and access this container without nginx-proxy at all - it works like expected.

Now I want to run it with nginx-proxy in front of it, but despite my efforts I get error 502 Bad Gateway. I must be missing something. What I've done:

1. I put VIRTUAL_HOST=mydomain.local, VIRTUAL_PROTO=https and VIRTUAL_PORT=443 in docker-compose.yml
2. When I run nginx-proxy container, I gave it a volume of .crt and .key files named "mydomain.local.crt" and "mydomain.local.key"

Should I do something else? What could be causing the 502 Bad Gateway?
There are no errors in nginx's access/error logs (it's configured to "debug" level). So how can I debug this?

This is the nginx config file:

server {
    listen 80;
    return 301 https://$host$request_uri;
}

server {

    listen 443 ssl;
    listen [::]:443 ssl ipv6only=on;
    ssl_certificate /etc/ssl/certs/nginx-selfsigned.crt;
    ssl_certificate_key /etc/ssl/private/nginx-selfsigned.key;

    error_log  /var/www/storage/logs/nginx-error.log debug;
    access_log /var/www/storage/logs/nginx-access.log;

   # Omitted the rest for simplicity...
}

This is docker-compose.yml

version: '3'

services:

  nginx:
    build:
      context: ../
      dockerfile: ./docker/nginx/Dockerfile

    environment:
      - VIRTUAL_HOST=mydomain.local
      - VIRTUAL_PROTO=https
      - VIRTUAL_PORT=443

    volumes:
      - ${BASE_PATH}/public:/var/www/public
      - ${BASE_PATH}/storage/logs/nginx-error.log:/var/www/storage/logs/nginx-error.log
      - ${BASE_PATH}/storage/logs/nginx-access.log:/var/www/storage/logs/nginx-access.log

This is the command I used to generate self-signed certificate:

RUN openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/ssl/private/nginx-selfsigned.key -out /etc/ssl/certs/nginx-selfsigned.crt -subj "/"