Is it possible to have IP whitelisting using google GCP API Gateway?

I've been searching on google and keep getting referred to the VPC documentation https://cloud.google.com/vpc-service-controls/docs/set-up-private-connectivity but I don't think this will solve my problem. I'm trying to limit the IP address accessing my webhook function on GCP and I need to use API gateway (Apigee isn't an option at the moment for me). Any advice would be great!

If API Gateway isn't requirement, I propose you this solution:

• Update the ingress control of your function to set it internal_and_cloud_load_balancing to allow only traffic from your VPCs and the load balancers
• Then create a HTTPS external load balancer with a serverless NEG that point to your Cloud Functions
• Add Cloud Armor policies on your Load Balancer to filter IP sources.