Problems with Mapping Non-Standard Port

[plankconst]

I setup my Cabot docker container on Ubuntu 18.04 and a public IP address and port mapping to port: 8080. It all works fine with the following setup:

docker-compose-caddy.yml:

version: "2.1"

services:
  caddy:
    image: abiosoft/caddy
    ports:
      - '80:80'
      - '443:443'
    depends_on:
      - web
    volumes:
      - ./.caddy:/root/.caddy
      - ./conf/Caddyfile:/etc/Caddyfile

and docker-compose.yml:

version: "2.1"

services:
  web:
    extends:
      file: docker-compose-base.yml
      service: base
    command: sh -c "cabot migrate && gunicorn cabot.wsgi:application -b 0.0.0.0$
    ports:
      - '8080:5000'
    depends_on:
      - postgres
      - rabbitmq
    restart: always
    ...

However, when the server's Port 80 is used by another web application on my server and I want to map Cabot to port 8080 locally and then to 8080 publicly, it doesn't work.

In other words, the mapping would be:

Public Port 8080 --> Caddy Port 8080 --> Cabot 5000

I tried to change docker-compose-caddy.yml:

version: "2.1"

services:
  caddy:
    image: abiosoft/caddy
    ports:
      - '8080:80'
      - '443:443'
    depends_on:
      - web
    volumes:
      - ./.caddy:/root/.caddy
      - ./conf/Caddyfile:/etc/Caddyfile

I get this error:

Recreating 7bca6949339e_docker-cabot_caddy_1 ... error Recreating 7bca6949339e_docker-cabot_caddy_1 ...

ERROR: for 7bca6949339e_docker-cabot_caddy_1 Cannot start service caddy: driverCreating docker-cabot_worker_1 ... done eb631a2673cff2ea0982a77fef50c90c713b4e8ae75761afcee080d40f33): Bind for 0.0.0.0:Creating docker-cabot_beat_1 ... done

ERROR: for caddy Cannot start service caddy: driver failed programming

Am I configuring my configuration files correctly?