fix gitignore files
diff --git a/src/csharp/.gitignore b/src/csharp/.gitignore
index c064ff1..ae48956 100644
--- a/src/csharp/.gitignore
+++ b/src/csharp/.gitignore
@@ -5,3 +5,4 @@
 packages
 Grpc.v12.suo
 TestResult.xml
+*.nupkg