createConfig.go

package main

import (
	"bytes"
	admissionregistrationv1 "k8s.io/api/admissionregistration/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	"os"
	ctrl "sigs.k8s.io/controller-runtime"
)

func createMutationConfig(caCert *bytes.Buffer) {

	var (
		webhookNamespace, _ = os.LookupEnv("WEBHOOK_NAMESPACE")
		mutationCfgName, _  = os.LookupEnv("MUTATE_CONFIG")
		// validationCfgName, _ = os.LookupEnv("VALIDATE_CONFIG") Not used here in below code
		webhookService, _ = os.LookupEnv("WEBHOOK_SERVICE")
	)
	config := ctrl.GetConfigOrDie()
	kubeClient, err := kubernetes.NewForConfig(config)
	if err != nil {
		panic("failed to set go -client")
	}

	path := "/mutate"
	fail := admissionregistrationv1.Fail

	mutateconfig := &admissionregistrationv1.MutatingWebhookConfiguration{
		ObjectMeta: metav1.ObjectMeta{
			Name: mutationCfgName,
		},
		Webhooks: []admissionregistrationv1.MutatingWebhook{{
			Name: "mapplication.kb.io",
			ClientConfig: admissionregistrationv1.WebhookClientConfig{
				CABundle: caCert.Bytes(), // CA bundle created earlier
				Service: &admissionregistrationv1.ServiceReference{
					Name:      webhookService,
					Namespace: webhookNamespace,
					Path:      &path,
				},
			},
			Rules: []admissionregistrationv1.RuleWithOperations{{Operations: []admissionregistrationv1.OperationType{
				admissionregistrationv1.Create},
				Rule: admissionregistrationv1.Rule{
					APIGroups:   []string{"apps"},
					APIVersions: []string{"v1"},
					Resources:   []string{"deployments"},
				},
			}},
			FailurePolicy: &fail,
		}},
	}
  
	if _, err := kubeClient.AdmissionregistrationV1().MutatingWebhookConfigurations().Create(mutateconfig)
		err != nil {
		panic(err)
	}
}