title: Next.js: ComponentWillMount vs. getInitialProps
body: <p>I'm using <a href="https://github.com/zeit/next.js" rel="noreferrer">Next.js</a> for my React application because it has server side rendering. As I checked by log, both methods <code>ComponentWillMount</code> and <code>getInitialProps</code> both run on the server side. Are there any differences between those methods?</p>
  <p>When should I run in <code>ComponentWillMount</code> and when should I run in <code>getInitialProps</code>?</p>
  <p>I don't see Next.js mentions about this thing.</p>