Cannot map domain to cluster in GCP

I am just starting out with kubernetes. I have created a simple app which is working fine with the external IP address. It's a mongodb-express with mongo-db backend. I am trying to get a domain name mapped to it, instead of the IP address.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: mongo-express
  labels:
    app: mongo-express
spec:
  replicas: 1
  selector:
    matchLabels:
      app: mongo-express
  template:
    metadata:
      labels:
        app: mongo-express
    spec:
      containers:
      - name: mongo-express
        image: mongo-express
        ports:
        - containerPort: 8081
        env:
        - name: ME_CONFIG_MONGODB_ADMINUSERNAME
          etc
---
apiVersion: v1
kind: Service
metadata:
  name: mongo-express-service
spec:
  selector:
    app: mongo-express
  type: LoadBalancer  
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8081
      

This was a walk in the park with AWS. Simply created a zone and added the name servers to the domain name provider, however in GCP this does not work. I have created a zone in cloudDNS but cannot seem to map it to the cluster. The documentation is a bit complex for me to understand. Can someone help?

kubernetes              ClusterIP      10.28.0.1     <none>         443/TCP        51m
mongo-express-service   LoadBalancer   10.28.7.249   34.69.73.210   80:30055/TCP   42m
mongodb-service         ClusterIP      10.28.1.163   <none>         27017/TCP      45m

Cloud DNS config is the same as the route53 configuration. You can add the CName record or A record as per requirement.

For a simple use case, you can follow this document which is regarding adding static IP to DNS and mapping the domain.

As you have already exposed the service with type LoadBalancer you can follow from here

https://cloud.google.com/kubernetes-engine/docs/tutorials/configuring-domain-name-static-ip#configuring_your_domain_name_records

Make sure your Nameserver are set correctly

If your nameserver is Cloud DNS: Follow Cloud DNS Quickstart guide to configure DNS A record for your domain name with the reserved IP address of your application.

If your nameserver is another provider: Refer to your DNS service's documentation on setting DNS A records to configure your domain name. If you choose to use Cloud DNS instead, refer to Migrating to Cloud DNS.

Extra :

You can also use the external DNS to auto add the ingress records to Cloud DNS.

Example : https://github.com/kubernetes-sigs/external-dns/blob/master/docs/tutorials/gke.md