[VOL-2099] Modify backend to Monitor and report KVStore Liveness state

Added all Unit Tests for backend.go

Change-Id: If6a43a763f14a81f78968c4617702672c2ab7eac
diff --git a/go.mod b/go.mod
index 5549427..9d74066 100644
--- a/go.mod
+++ b/go.mod
@@ -38,6 +38,7 @@
 	golang.org/x/net v0.0.0-20190930134127-c5a3c61f89f3 // indirect
 	golang.org/x/sys v0.0.0-20191001151750-bb3f8db39f24 // indirect
 	golang.org/x/text v0.3.2 // indirect
+	google.golang.org/appengine v1.4.0 // indirect
 	google.golang.org/genproto v0.0.0-20190927181202-20e1ac93f88c // indirect
 	google.golang.org/grpc v1.24.0
 	gopkg.in/jcmturner/goidentity.v3 v3.0.0 // indirect