How to retrieve firebase access token on server?

[serendipity1004]

I am currently trying out the with-firebase-auth example to implement firebase authentication in NextJS app. It's working great except when I run a server side rendering. When I need to fetch some remote data (that is not NextJS API endpoint) I need to embed firebase access token so that the request can be verified. But since I am not able to retrieve the token on the server side, I am unable to use the token when retrieving data during getServerSideProps. How can I overcome this problem?