Here is a list of the most used and up-to-date OAuth2 Client libraries that you can use in your project.
https://github.com/ssofy/javascript-sdk
https://github.com/openid/AppAuth-JS
https://github.com/lelylan/simple-oauth2
https://github.com/ssofy/php-sdk
https://oauth2-client.thephpleague.com
https://authomatic.github.io/authomatic
https://github.com/golang/oauth2
https://github.com/openid/AppAuth-Android