title: Angular 2 Cancelling Route Navigation on UnAuthenticate
body: <p>I have an app, with 3 links: Home (/), Sign in (/user/sign-in) and User Detail (/user).</p>
  
  <p>When user click Home, my app will be show content public</p>
  
  <p>When user click User Detail, my app will be show popup sign in, if user cancel sign in popup, my app will be keep current location, not change to /user.</p>
  
  <p>But i don't know detect route change start event and cancel this. Please help me. Thanks.</p>