code: function registerFavicon(app, config) {
      if (typeof config.static !== 'string' || !config.static) return;
      let stat;
      // check .ico
      try {
        stat = fs.lstatSync(config.static + '/favicon.ico');
        if (stat.isFile()) return;
      } catch (e) {
        if (e.code !== 'ENOENT') return;
      }
      let faviconFn = initFavicon(thorin, config);
      if (!faviconFn) return;
      app.use(faviconFn);
    }
docs: /* Check favicon middleware