Allow to tap multiple function services at one time (#1434)

The router taps function service one by one which is inefficient and
increases the burden of executor. This PR aggregates all requests into
one to solve the problem mentioned above.

pkg/router/functionHandler_test.go

@@ -57,12 +57,12 @@ func TestFunctionProxying(t *testing.T) {
 	backendURL := createBackendService(testResponseString)
 	log.Printf("Created backend svc at %v", backendURL)
 
-	fn := &metav1.ObjectMeta{Name: "foo", Namespace: metav1.NamespaceDefault}
+	fnMeta := metav1.ObjectMeta{Name: "foo", Namespace: metav1.NamespaceDefault}
 	logger, err := zap.NewDevelopment()
 	panicIf(err)
 
 	fmap := makeFunctionServiceMap(logger, 0)
-	fmap.assign(fn, backendURL)
+	fmap.assign(&fnMeta, backendURL)
 
 	httpTrigger := &fv1.HTTPTrigger{
 		Metadata: metav1.ObjectMeta{
@@ -78,9 +78,11 @@ func TestFunctionProxying(t *testing.T) {
 	}
 
 	fh := &functionHandler{
-		logger:   logger,
-		fmap:     fmap,
-		function: fn,
+		logger: logger,
+		fmap:   fmap,
+		function: &fv1.Function{
+			Metadata: metav1.ObjectMeta{Name: "foo", Namespace: metav1.NamespaceDefault},
+		},
 		tsRoundTripperParams: &tsRoundTripperParams{
 			timeout:         50 * time.Millisecond,
 			timeoutExponent: 2,