message: fix async examples
diff: @@ -20,6 +20,7 @@ it('works with async/await', async () => {
  // Testing for async errors can be done using `catch`.
  it('tests error with promises', () => {
  + expect.assertions(1);
  return user.getUserName(3)
  .catch(e => expect(e).toEqual({
  error: 'User with 3 not found.',
  @@ -28,6 +29,7 @@ it('tests error with promises', () => {
  // Or try-catch.
  it('tests error with async/await', async () => {
  + expect.assertions(1);
  try {
  await user.getUserName(2);
  } catch (object) {
  