VOL-2076 Unit Test cases for core.go

Change-Id: Ie003cd248478679404107d985c1a22a381e6348c
diff --git a/go.mod b/go.mod
index 63657f9..18c1ed6 100644
--- a/go.mod
+++ b/go.mod
@@ -10,6 +10,7 @@
 	github.com/gyuho/goraph v0.0.0-20160328020532-d460590d53a9
 	github.com/opencord/voltha-lib-go/v2 v2.2.7
 	github.com/opencord/voltha-protos v1.0.3
+	github.com/phayes/freeport v0.0.0-20180830031419-95f893ade6f2
 	github.com/stretchr/testify v1.4.0
 	google.golang.org/grpc v1.24.0
 )