Variables in config in Caddyfile. Note usage of (dev) and (prod)
Github issue reference

  :80

(dev) {
    handle_path /* {
        reverse_proxy nextjs:3000

    }
}

(prod) {
    handle_path /* {
        file_server
        root * /app
    }
}

import {$CADDY_MODE:prod}

handle_path /spec/* {
    file_server
    root * /public/spec
}

handle_path /api/* {
    reverse_proxy mock:4010
}