Clarify that TLS+gRPC is not supported by Go Client

kuksa_go_client/README.md

@@ -65,7 +65,9 @@ The GO clients reads the configuration file `kuksa-client.json`. In this reposit
 KUKSA.val Databroker (`kuksa-client-grpc.json`) and KUKSA.val Server (`kuksa-client-ws.json`) exists.
 The file `kuksa-client.json` is by default linked to `kuksa-client-grpc.json`.
 
-For using the GO client with the kuksa.val server set protocol = ws and for a connection to kuksa.val databroker set protocol = grpc. On the command line it's available through -protocol ws/grpc.
+For using the GO client with the kuksa.val server set protocol = ws and for a connection to kuksa.val Databroker set protocol = grpc. On the command line it's available through -protocol ws/grpc.
+
+*Note: For communication with KUKSA Databroker only insecure mode is supported, TLS can not be used!*
 
 ### Dependency updates
 

kuksa_go_client/kuksa_client/commn.go

@@ -61,6 +61,9 @@ const (
 
 func (cg *KuksaClientCommGrpc) startCommunication() error {
 	var opts []grpc.DialOption
+	if !cg.Config.Insecure {
+		return errors.New("TLS not supported for communication with KUKSA Databroker!")
+	}
 	opts = append(opts, grpc.WithTransportCredentials(insecure.NewCredentials()))
 	serverUrl := cg.Config.ServerAddress + ":" + cg.Config.ServerPort
 	var err error