401 Unauthorized while running the application

[saipraveen-a]

Followed the steps in the readme to setup the clientId and clientSecret for my app from the google developer console. However, there is a 401 error

This application has no explicit mapping for /error, so you are seeing this as a fallback.
There was an unexpected error (type=Unauthorized, status=401).
Authentication Failed: Could not obtain access token

The authorization code is sent as a param to the redirect url; it looks like the step to fetch the token from the code is failing. Not sure about the reason.
Please let me know what is the issue and how to resolve this

http://localhost:8080/login?state=lPUTMz&code=4/AAABGwcvimYggXTgS_PE_FA0Kj5yC51BMDbWwMtoHapeF3KV0ZlSQ65fMZymLE6KUkMyNp_4US1pn7eW2UKU5g0&authuser=0&session_state=916976b3d98f07bb514aee7cd69208b78ec0c762..b804&prompt=consent#