Watching for any Istio CRD updates (add,delete,update) in Go

main.go

package main

import (
  "fmt"
  "flag"
  "time"
  
  "istio.io/client-go/pkg/apis/networking/v1alpha3"
  "sigs.k8s.io/controller-runtime/pkg/client/config"
  versionedclient "istio.io/client-go/pkg/clientset/versioned"
  "k8s.io/api/core/v1"
  "k8s.io/apimachinery/pkg/fields"
  "k8s.io/client-go/util/workqueue"
  "k8s.io/client-go/kubernetes"
  "k8s.io/client-go/tools/cache"
  "k8s.io/client-go/tools/clientcmd"
)

func main() {
  // initialize config
  config, err := clientcmd.BuildConfigFromFlags("", "")
    if err != nil {
        panic(err.Error())
    }
    // k8s clientset
    clientset, err := kubernetes.NewForConfig(config)
    if err != nil {
       panic(err.Error())
    }
    // istio clientset
    resourceClientSet, err := versionedclient.NewForConfig(config)
    if err != nil {
      panic(err.Error())
    }
    // initialize a workqueue
    queue := workqueue.NewRateLimitingQueue(workqueue.DefaultControllerRateLimiter())
  
    // watch for all service entry events
    watchlist := cache.NewListWatchFromClient(
        resourceClientSet.NetworkingV1alpha3().RESTClient(),
        string("serviceentries"),
        v1.NamespaceAll,
        fields.Everything(),
    )
    _, controller := cache.NewInformer( 
        watchlist,
        &v1.Service{},
        0, //Duration is int64
        cache.ResourceEventHandlerFuncs{
            AddFunc: func(obj interface{}) {
                o, ok := obj.(*v1alpha3.ServiceEntry)
                if ok {
                  // do stuff
                  // add it to a queue for later processing
                  queue.Add(o)
                }
                fmt.Printf("service added: %v \n", obj)
            },
            DeleteFunc: func(obj interface{}) {
                o, ok := obj.(*v1alpha3.ServiceEntry)
                if ok {
                  // do stuff
                  fmt.Printf("service deleted: %v", obj)
                }
            },
            UpdateFunc: func(oldObj, newObj interface{}) {
                o, ok := obj.(*v1alpha3.ServiceEntry)
                if ok {
                  // do stuff
                  fmt.Printf("service changed %v", obj)
                }
            },
         },
     )
    // create a stop channel
    stop := make(chan struct{})
    defer close(stop)
    go controller.Run(stop)
    // run forever
    for {
      time.Sleep(time.Second)
    }
}