it works!

config.toml

@@ -0,0 +1,17 @@
+listen_url = "http://localhost:3000"
+guarded_paths = ["/"]
+# A list of all allowed users. For GitHub it is a list of usernames.
+# For Google it is a list of emails
+allowed_users = ["lukasmwerner"]
+
+[upstream]
+addr = "http://localhost:8080"
+# An optional program to run as the upstream
+program = "rezepte"
+args = []
+
+[provider]
+kind = "github" # can `google` or `github`
+client_id = "<CHANGE_ME>"
+client_secret = "<CHANGE_ME>"
+redirect_url = "http://localhost:3000/oauth/callback"