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

person.go

@@ -15,7 +15,10 @@ type Person struct {
 
 // NewPerson creates a new Person. It returns a *Person.
 func NewPerson(name string) *Person {
-	return &Person{Name: name}
+	return &Person{
+		CommonAttributes: newCommonAttributes(),
+		Name:             name,
+	}
 }
 
 // AddExtension adds the Extension to the Person.