How to pass OAuth token to userinfo URL?

I’m trying to set up Generic OAuth with Phabricator as server.

Phabricator requires me to pass the access token to the userinfo URL, thus the link should look like

https://phabricator.example.com/api/user.whoami?access_token=<TOKEN>

My current environment contains

CONCOURSE_OAUTH_AUTH_URL=https://phabricator.example.com/oauthserver/auth/
CONCOURSE_OAUTH_TOKEN_URL=https://phabricator.example.com/oauthserver/token/
CONCOURSE_OAUTH_USERINFO_URL=https://phabricator.example.com/api/user.whoami

How can I let Concourse pass the token to the userinfo URL?