How to change the language code URL?

[nordkite]

How can I change language URL? Right now when switching language we have

mysite.com/about?language-picker-language=en

But I need

mysite.com/about/en

When I switch a language I get
Setting unknown property: app\models\User::language but site language is changed because when I go to Homepage for example after error Yii::$app->language show the language I clicked previously.

[lajax]

This issue belongs to the framework, the urlManager need to be overwritten.
In the next version I will make it to an optional option.