Caddy + xcaddy within a docker container

Start Caddy within a docker container and add a plugin.

https://caddyserver.com/docs/modules/security

./docker-compose.yml

version: '3.4'
networks:
  monitor-net:
    driver: bridge
volumes:
    caddy_data: {}
services:
  caddy:
    # cf. https://github.com/caddyserver/caddy/releases
    # image: caddy:2.5.0
    build:
      context: ./caddy/ # where to look for the Dockerfile
      dockerfile: Dockerfile # actual name of the Dockerfile
      args:
        image_ref: caddy:2.5.0
    container_name: caddy
    ports:
      - "80:80"
      - "443:443"
    volumes:
      - ./caddy:/etc/caddy
      - caddy_data:/data
    env_file:
      ./.env
    restart: unless-stopped
    networks:
      - monitor-net
    labels:
      org.label-schema.group: "monitoring"

image_ref: caddy:2.5.0 # image reference used twice in the Dockerfile, once with ${image_ref}-builder, once directly

./caddy/Dockerfile :

ARG image_ref
FROM ${image_ref}-builder AS caddy-build
RUN xcaddy build --with github.com/greenpau/caddy-security
FROM ${image_ref}
COPY --from=caddy-build /usr/bin/caddy /usr/bin/caddy

Caddyfile must exist (content not relevant here):

./caddy/Caddyfile

command :

docker-compose  up --build caddy