Instanciate common attributes everywhere so one can simply use the extend method

id.go

@@ -14,7 +14,10 @@ type ID struct {
 
 // NewID creates a new ID. It returns a *ID.
 func NewID(uri string) *ID {
-	return &ID{URI: uri}
+	return &ID{
+		CommonAttributes: newCommonAttributes(),
+		URI:              uri,
+	}
 }
 
 // Check checks the ID for incompatibilities with RFC4287. It returns an error.