Caddyfile v2 example

Caddyfile

yourdomain.com {
  tls email@abc.com
  root * /srv/www
  file_server

  handle_errors {
      @404 {
          expression int({http.error.status_code}) == 404
      }
      respond @404 "This is 404 error message"
  }

  @ws {
    header Connection Upgrade
    header Upgrade websocket
  }
  reverse_proxy @ws localhost:6443
}