Add volume id lookup caching

go/operation/lookup_vid_cache_test.go

@@ -0,0 +1,26 @@
+package operation
+
+import (
+	"fmt"
+	"testing"
+	"time"
+)
+
+func TestCaching(t *testing.T) {
+	var (
+		vc VidCache
+	)
+	var locations []Location
+	locations = append(locations, Location{Url: "a.com:8080"})
+	vc.Set("123", locations, time.Second)
+	ret, _ := vc.Get("123")
+	if ret == nil {
+		t.Fatal("Not found vid 123")
+	}
+	fmt.Printf("vid 123 locations = %v\n", ret)
+	time.Sleep(2 * time.Second)
+	ret, _ = vc.Get("123")
+	if ret != nil {
+		t.Fatal("Not found vid 123")
+	}
+}