Set modified via bson marshal and update operators

storage/operator/modify.go

@@ -2,6 +2,8 @@ package operator
 
 import (
 	"fmt"
+	"local/whodunit/storage/entity"
+	"time"
 
 	"go.mongodb.org/mongo-driver/bson"
 )
@@ -51,9 +53,16 @@ func opMarshalable(op, key string, value interface{}) map[string]map[string]inte
 	if len(key) == 0 {
 		return nil
 	}
-	return map[string]map[string]interface{}{
+	m := map[string]map[string]interface{}{
 		op: map[string]interface{}{
 			key: value,
 		},
 	}
+	if _, ok := m["$set"]; !ok {
+		m["$set"] = map[string]interface{}{}
+	}
+	if _, ok := m["$set"][entity.Modified]; !ok {
+		m["$set"][entity.Modified] = time.Now().UnixNano()
+	}
+	return m
 }