nginx reverse proxy nodejs - node.js

Question

I want:
(1) https://example.com to serve static content using SSL
(2) https://sub.example.com/myapp to serve dynamic content from NodeJS using SSL.
I have a domain example.com and one subdomain sub.example.com. I have a Docker container that has nginx and a nodejs app in it. Using Ubuntu on Digital Ocean.
I am getting 502 Bad Gateway errors. Not sure if this CAN work or if it can, how to fix it.
The nodejs app listens on 8080 (no host specified, no SSL)
Nginx listens on 80 and 443 for example.com but redirects all http (80) requests to https (443)
Nginx listens on 443 for sub.example.com.
docker-compose.yml:
version: '3'
services:
nginx:
image: nginx:1.15-alpine
restart: unless-stopped
volumes:
- ./data/nginx:/etc/nginx/conf.d
- ./data/certbot/conf:/etc/letsencrypt
- ./data/certbot/www:/var/www/certbot
- ./data/nginx/html:/etc/nginx/html
ports:
- "80:80"
- "443:443"
command: "/bin/sh -c 'while :; do sleep 6h & wait $${!}; nginx -s reload; done & nginx -g \"daemon off;\"'"
certbot:
image: certbot/certbot
restart: unless-stopped
volumes:
- ./data/certbot/conf:/etc/letsencrypt
- ./data/certbot/www:/var/www/certbot
entrypoint: "/bin/sh -c 'trap exit TERM; while :; do certbot renew; sleep 12h & wait $${!}; done;'"
node:
image: node:11
volumes:
- ./data/node:/usr/local/src/node
ports:
- "8080:8080"
working_dir: /usr/local/src/node/myapp
command: node server.js
nginx.conf:
server {
listen 80;
server_name example.com;
server_tokens off;
location /.well-known/acme-challenge/ {
root /var/www/certbot;
}
location / {
return 301 https://$host$request_uri;
}
}
server {
listen 443 ssl;
server_name example.com;
server_tokens off;
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
include /etc/letsencrypt/options-ssl-nginx.conf;
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem;
location /myapp {
proxy_pass http://localhost:8080;
}
}