How to use the umi-core/lib/getUserConfig function in umi-core

export default function(cwd) {
  registerBabel(cwd);
  const config = getUserConfig({ cwd });

  if (config.ssr) return false;

  if (process.env.BIGFISH_COMPAT) {
    if (config.appType !== 'console') return false;
    if (config.deployMode === 'chair') return false;
  }

  const pkgFile = join(cwd, 'package.json');
  const pkg = existsSync(pkgFile) ? JSON.parse(readFileSync(pkgFile, 'utf-8')) : {};

  // disable if react is lower than 16
  const reactVersion = getDep(pkg, 'react');
  if (reactVersion) {
    const reactPkgFile = join(cwd, 'node_modules', 'react', 'package.json');
    const reactPkg = existsSync(reactPkgFile)

static getConfig(opts = {}) {
    const { cwd, service } = opts;
    return getUserConfig({
      cwd,
      defaultConfig: service.applyPlugins('modifyDefaultConfig', {
        initialValue: {},
      }),
    });
  }