Use in-cluster config directly when config flags are not set.

Eliminates a warning message at startup.

cmd/main.go

@@ -48,6 +48,7 @@ import (
 	api_v1 "k8s.io/api/core/v1"
 	"k8s.io/client-go/informers"
 	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
 )
 
@@ -245,9 +246,16 @@ func main() {
 		os.Exit(-1)
 	}
 
-	config, err := clientcmd.BuildConfigFromFlags(*masterURLF, *kubeconfigF)
-	if err != nil {
-		log.Fatalf("error creating client configuration: %v", err)
+	var config *rest.Config
+	if *masterURLF == "" && *kubeconfigF == "" {
+		if config, err = rest.InClusterConfig(); err != nil {
+			log.Fatalf("error creating in-cluster config: %v", err)
+		}
+	} else if config, err = clientcmd.BuildConfigFromFlags(*masterURLF,
+		*kubeconfigF); err != nil {
+		log.Fatalf("error creating client config from "+
+			"masterURL=%s and kubeconfig=%s: %v",
+			*masterURLF, *kubeconfigF, err)
 	}
 	kubeClient, err := kubernetes.NewForConfig(config)
 	if err != nil {