Support connecting to multiple OpenFlow controllers

Change-Id: I0989d5031fb2d4f5aa78ba0e4576e465f826a419
diff --git a/go.mod b/go.mod
index f8a6395..f695b36 100644
--- a/go.mod
+++ b/go.mod
@@ -7,6 +7,7 @@
 	github.com/golang/protobuf v1.3.2
 	github.com/opencord/voltha-lib-go/v3 v3.0.23
 	github.com/opencord/voltha-protos/v3 v3.2.3
+	github.com/stretchr/testify v1.4.0
 	golang.org/x/net v0.0.0-20191112182307-2180aed22343
 	google.golang.org/grpc v1.25.1
 )