You might heard about shibboleth and their great solutions as for Identity Provider (https://shibboleth.net/products/identity-provider.html) so is for Service Provider (e.g. nginx https://github.com/nginx-shib/nginx-http-shibboleth).
It's known that Google offers its own SAML2 IDP and we want to use it:
nginx needs to know what user from google is in order to proceed with website. Was possible to do that on that tier with shibboleth, but I have quite hard times finding solutions with Google.
Anybody has some ideas? Thank you!