Grafana config with CAS Auth

Hello,
I installed the latest stable version from Grafana 7.2. Now, I want to add SSO CAS auth to grafana but I don’t know how to config custom.ini in grafana conf.
I already have CAS server.
My cas sso using mod_cas (via http://www.apereo.org/cas).
My login url:
https://xxx.com/cas/login?service=${myServiceUrl}
After redirect and login, my url return:
myServiceUrl?ticket=${ticket}
A request like:
https://xxx.com/cas/serviceValidate?ticket=${ticket}&service=${myServiceUrl}
was sent to get xml cas:user username.
How can I config my grafana to auth with cas sso?
I have read many post about this but don’t have any solution. Please help me.
Thank you.