Unable to use OAuth for Google, getting some error in expressJS

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Actual behavior

Google OAuth is not working with some error in express. A full error log is pasted below.

Error: Can't set headers after they are sent

Expected behavior

Google auth should work if a user has been added

Steps to reproduce the behavior

When trying to use Google OAuth getting the following error:

https://pastebin.com/fMMFE0Dz