fix(dashboard): resolve --kubeconfig flag conflict with controller-runtime

Context: discovered the binary panicked on startup with "flag redefined: kubeconfig"
when testing locally. controller-runtime/pkg/client/config registers --kubeconfig
in its init() function; our manual flag.String("kubeconfig") caused a duplicate.
Fixed by removing the manual flag and using ctrlcfg.GetConfig() instead, which
already reads the controller-runtime-registered flag.

Author: tazhate

cmd/dashboard/main.go

@@ -6,7 +6,7 @@
 //
 //	--port       int      HTTP listen port (default 8090)
 //	--namespace  string   Namespace to watch; empty = all namespaces
-//	--kubeconfig string   Path to kubeconfig; empty = in-cluster
+//	--kubeconfig string   Path to kubeconfig (registered by controller-runtime)
 //	--refresh    duration Cache refresh interval (default 15s)
 package main
 
@@ -22,30 +22,29 @@ import (
 	"time"
 
 	k8sruntime "k8s.io/apimachinery/pkg/runtime"
-	"k8s.io/client-go/rest"
-	"k8s.io/client-go/tools/clientcmd"
 	"sigs.k8s.io/controller-runtime/pkg/client"
+	ctrlcfg "sigs.k8s.io/controller-runtime/pkg/client/config"
 
 	v1alpha1 "github.com/tazhate/blockchain-node-operator/api/v1alpha1"
 	"github.com/tazhate/blockchain-node-operator/internal/dashboard"
 )
 
 func main() {
 	var (
-		port       = flag.Int("port", 8090, "HTTP listen port")
-		namespace  = flag.String("namespace", "", "Namespace to watch (empty = all)")
-		kubeconfig = flag.String("kubeconfig", "", "Path to kubeconfig (empty = in-cluster)")
-		refresh    = flag.Duration("refresh", 15*time.Second, "Cache refresh interval")
+		port      = flag.Int("port", 8090, "HTTP listen port")
+		namespace = flag.String("namespace", "", "Namespace to watch (empty = all)")
+		refresh   = flag.Duration("refresh", 15*time.Second, "Cache refresh interval")
 	)
 	flag.Parse()
 
-	cfg, err := buildRestConfig(*kubeconfig)
+	// --kubeconfig is registered by sigs.k8s.io/controller-runtime/pkg/client/config init().
+	// ctrlcfg.GetConfig() reads that flag automatically.
+	restCfg, err := ctrlcfg.GetConfig()
 	if err != nil {
 		log.Fatalf("build rest config: %v", err)
 	}
 
-	scheme := buildScheme()
-	k8sClient, err := client.New(cfg, client.Options{Scheme: scheme})
+	k8sClient, err := client.New(restCfg, client.Options{Scheme: buildScheme()})
 	if err != nil {
 		log.Fatalf("build k8s client: %v", err)
 	}
@@ -59,7 +58,6 @@ func main() {
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
 	defer stop()
 
-	// Start cache refresh loop in background.
 	go srv.Start(ctx)
 
 	httpSrv := &http.Server{
@@ -86,20 +84,6 @@ func main() {
 	}
 }
 
-func buildRestConfig(kubeconfig string) (*rest.Config, error) {
-	if kubeconfig != "" {
-		return clientcmd.BuildConfigFromFlags("", kubeconfig)
-	}
-	cfg, err := rest.InClusterConfig()
-	if err == nil {
-		return cfg, nil
-	}
-	loadingRules := clientcmd.NewDefaultClientConfigLoadingRules()
-	return clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
-		loadingRules, &clientcmd.ConfigOverrides{},
-	).ClientConfig()
-}
-
 func buildScheme() *k8sruntime.Scheme {
 	s := k8sruntime.NewScheme()
 	if err := v1alpha1.AddToScheme(s); err != nil {