Use common httpserver across fission (#2409)

* Defining httpserver package to capture httpserver shutdown and
introduces uniform running of http server across codebase.
* Add unit tests for httpserver

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>

pkg/router/mutablemux_test.go

@@ -17,6 +17,7 @@ limitations under the License.
 package router
 
 import (
+	"context"
 	"log"
 	"net/http"
 	"testing"
@@ -26,6 +27,7 @@ import (
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
 
+	"github.com/fission/fission/pkg/utils/httpserver"
 	"github.com/fission/fission/pkg/utils/metrics"
 )
 
@@ -47,13 +49,6 @@ func verifyRequest(expectedResponse string) {
 	testRequest(targetURL, expectedResponse)
 }
 
-func startServer(mr *mutableRouter) {
-	err := http.ListenAndServe(":3333", mr)
-	if err != nil {
-		log.Fatal(err)
-	}
-}
-
 func spamServer(quit chan bool) {
 	i := 0
 	for {
@@ -83,10 +78,10 @@ func TestMutableMux(t *testing.T) {
 	panicIf(err)
 
 	mr := newMutableRouter(logger, muxRouter)
-
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
 	// start http server
-	log.Print("Start http server")
-	go startServer(mr)
+	go httpserver.StartServer(ctx, logger, "router", "3333", mr)
 
 	// continuously make requests, panic if any fails
 	time.Sleep(100 * time.Millisecond)
@@ -102,7 +97,7 @@ func TestMutableMux(t *testing.T) {
 	// change the muxer
 	log.Print("Change mux router")
 	newMuxRouter := mux.NewRouter()
-	muxRouter.Use(metrics.HTTPMetricMiddleware())
+	newMuxRouter.Use(metrics.HTTPMetricMiddleware())
 	newMuxRouter.HandleFunc("/", NewHandler)
 	mr.updateRouter(newMuxRouter)