Caddyfile

# domain name.
localhost:8080

# Set this path to your site's directory.
root * /io/www/html

# Enable the static file server.
file_server

# localhost:8080/ows/AV_TH_V1?SERVICE=wms
# directly call QGIS via fcgi
reverse_proxy qgisserver:9993 {
    transport fastcgi {
        env QUERY_STRING {query}&map=/io/data/{http.regexp.map_file.1}.qgs
        env PGSERVICEFILE /io/.pg_service.conf
        # fastcgi_param PGSERVICEFILE /io/.pg_service.conf;
    }
}