https://github.com/udhos/groupcache_oauth2 implements the oauth2 client_credentials flow cacheing tokens with groupcache.
FIXME WRITEME
See cmd/groupcache-oauth2-client-example/main.go.
Test using this token server: https://oauth.tools/collection/1599045253169-GHF
go install github.com/udhos/oauth2/cmd/groupcache-oauth2-client-example@latest
groupcache-oauth2-client-example -tokenURL https://login-demo.curity.io/oauth/v2/oauth-token -clientID demo-backend-client -clientSecret MJlO3binatD9jk1
git clone https://github.com/udhos/groupcache_oauth2
cd groupcache_oauth2
./build.sh