VOL-2788 update voltha-go to latest voltha-lib-go and release

Change-Id: I853955d5ad3d84bae8b7b52e676872171c9ffe67
diff --git a/go.mod b/go.mod
index 9f3a469..d696801 100644
--- a/go.mod
+++ b/go.mod
@@ -6,7 +6,7 @@
 	github.com/gogo/protobuf v1.3.0
 	github.com/golang/protobuf v1.3.2
 	github.com/google/uuid v1.1.1
-	github.com/opencord/voltha-lib-go/v3 v3.0.15
+	github.com/opencord/voltha-lib-go/v3 v3.0.20
 	github.com/opencord/voltha-protos/v3 v3.2.6
 	github.com/phayes/freeport v0.0.0-20180830031419-95f893ade6f2
 	github.com/stretchr/testify v1.4.0