How to use the webdriverio/build/lib/launcher function in webdriverio

return new Promise((resolve, reject) => {
            $.util.log($.util.colors.blue(`Launching WebdriverIO for ${browsers[j]}...`));
            $.util.log($.util.colors.blue(specs));
            const wdio = new WebdriverIOLauncher('core/test/e2e-webdriverio/wdio.conf.js');
            wdio.run()
            .then(
              function (exitCode) {
                const exitMessage = `WebdriverIO has exited with ${exitCode}`;

                switch (exitCode) {
                  case 0: // success
                    $.util.log($.util.colors.green(exitMessage));
                    $.util.log($.util.colors.green('Passed E2E tests successfully.'));
                    break;
                  default: // error
                    $.util.log($.util.colors.red(exitMessage));
                    $.util.log($.util.colors.red('Failed to pass some E2E tests. (Otherwise, the E2E testing itself is broken)'));
                    testsPassed = false;
                }
                resolve();