diff --git a/readme.md b/readme.md
index 06ca5b7..7a409c8 100644
--- a/readme.md
+++ b/readme.md
@@ -9,7 +9,6 @@
 
 mvp
 
-* refactor cards/set to scryfall.go
 * refactor storage to have a storage object.
 * single view for card, with history
 * docker with local mounted volume and git ignore
diff --git a/src/serra/root.go b/src/serra/root.go
index 14a5c8d..56b35ad 100644
--- a/src/serra/root.go
+++ b/src/serra/root.go
@@ -17,7 +17,7 @@ func Add(cards []string) {
 	LogMessage(fmt.Sprintf("Serra %v\n", version), "green")
 
 	client := storage_connect()
-	coll := client.Database("serra").Collection("cards")
+	coll := &Collection{client.Database("serra").Collection("cards")}
 
 	// Loop over different cards
 	for _, card := range cards {
@@ -29,7 +29,7 @@ func Add(cards []string) {
 		}
 
 		// Write card to mongodb
-		err = storage_add(coll, c)
+		err = coll.storage_add(c)
 		if err != nil {
 			LogMessage(fmt.Sprintf("%v", err), "red")
 			continue
@@ -45,11 +45,11 @@ func Cards() {
 	LogMessage(fmt.Sprintf("Serra %v\n", version), "green")
 
 	client := storage_connect()
-	coll := client.Database("serra").Collection("cards")
+	coll := &Collection{client.Database("serra").Collection("cards")}
 
 	sort := bson.D{{"collectornumber", 1}}
 	filter := bson.D{{}}
-	cards, _ := storage_find(coll, filter, sort)
+	cards, _ := coll.storage_find(filter, sort)
 
 	for _, card := range cards {
 		fmt.Printf("%s (%s) %.2f\n", card.Name, card.Set, card.Prices.Eur)
@@ -61,7 +61,7 @@ func Sets() {
 	LogMessage(fmt.Sprintf("Serra %v\n", version), "green")
 
 	client := storage_connect()
-	coll := client.Database("serra").Collection("cards")
+	coll := &Collection{client.Database("serra").Collection("cards")}
 
 	groupStage := bson.D{
 		{"$group", bson.D{
@@ -72,7 +72,7 @@ func Sets() {
 		}},
 	}
 
-	sets, _ := storage_aggregate(coll, groupStage)
+	sets, _ := coll.storage_aggregate(groupStage)
 	for _, set := range sets {
 		fmt.Printf("* %s (%.2f Eur)\n", set["_id"], set["sum"])
 	}
@@ -84,11 +84,11 @@ func Update() {
 	LogMessage(fmt.Sprintf("Serra %v\n", version), "green")
 
 	client := storage_connect()
-	coll := client.Database("serra").Collection("cards")
+	coll := &Collection{client.Database("serra").Collection("cards")}
 
 	sort := bson.D{{"_id", 1}}
 	filter := bson.D{{}}
-	cards, _ := storage_find(coll, filter, sort)
+	cards, _ := coll.storage_find(filter, sort)
 
 	for i, card := range cards {
 		fmt.Printf("Updating (%d/%d): %s (%s)...\n", i+1, len(cards), card.Name, card.SetName)
@@ -114,7 +114,7 @@ func Update() {
 			"$push": bson.M{"serra_prices": bson.M{"date": primitive.NewDateTimeFromTime(time.Now()),
 				"value": updated_card.Prices.Eur}}}
 
-		storage_update(coll, filter, update)
+		coll.storage_update(filter, update)
 	}
 
 	storage_disconnect(client)
diff --git a/src/serra/storage.go b/src/serra/storage.go
index 8f1b81a..8fcdffd 100644
--- a/src/serra/storage.go
+++ b/src/serra/storage.go
@@ -12,6 +12,11 @@ import (
 	"go.mongodb.org/mongo-driver/mongo/options"
 )
 
+// https://siongui.github.io/2017/02/11/go-add-method-function-to-type-in-external-package/
+type Collection struct {
+	*mongo.Collection
+}
+
 func storage_connect() *mongo.Client {
 
 	uri := os.Getenv("MONGODB_URI")
@@ -27,7 +32,7 @@ func storage_connect() *mongo.Client {
 	return client
 }
 
-func storage_add(coll *mongo.Collection, card *Card) error {
+func (coll Collection) storage_add(card *Card) error {
 
 	card.SerraUpdated = primitive.NewDateTimeFromTime(time.Now())
 
@@ -39,7 +44,7 @@ func storage_add(coll *mongo.Collection, card *Card) error {
 
 }
 
-func storage_find(coll *mongo.Collection, filter, sort bson.D) ([]Card, error) {
+func (coll Collection) storage_find(filter, sort bson.D) ([]Card, error) {
 
 	opts := options.Find().SetSort(sort)
 	cursor, err := coll.Find(context.TODO(), filter, opts)
@@ -56,7 +61,7 @@ func storage_find(coll *mongo.Collection, filter, sort bson.D) ([]Card, error) {
 
 }
 
-func storage_aggregate(coll *mongo.Collection, groupstage bson.D) ([]primitive.M, error) {
+func (coll Collection) storage_aggregate(groupstage bson.D) ([]primitive.M, error) {
 
 	// db.cards.aggregate([ {$group: { _id: "$setname", sum: { $sum: "$prices.eur"}}}])
 	opts := options.Aggregate().SetMaxTime(2 * time.Second)
@@ -78,7 +83,7 @@ func storage_aggregate(coll *mongo.Collection, groupstage bson.D) ([]primitive.M
 
 }
 
-func storage_update(coll *mongo.Collection, filter, update bson.M) error {
+func (coll Collection) storage_update(filter, update bson.M) error {
 
 	// Call the driver's UpdateOne() method and pass filter and update to it
 	_, err := coll.UpdateOne(