GKE, change default cluster domain from "cluster.local" to public domain like "mycompany.com"

I have created a standard GKE cluster, I want to change default domain “cluster.local” to something which is accessible from internet so that I can implement IMS (project clearwater) to be accessible on internet.

Cluster information:

Kubernetes version: 1.12-1.13
Cloud being used: GCP
Installation method: GKE

You need to expose your application using either a Type LoadBalancer or NodePort Service or use an Ingress that will deploy a Google Global Load Balancer.

Check this documentation for more information Using a Service to Expose Your App - Kubernetes.