title: How to check whether the access token is expired or not?
body: <p>I am following Oauth 2.0 authentication protocol.</p>
  
  <p>There, it's said in the Authorization code flow after getting the Oauth Access token we need to refresh it using the refresh token if Access_toke is expired.</p>
  
  <p>My question is how do we know whether the access_token is expired or not?. so that we can claim a new access token with the help of refresh_token.</p>