Reassign or refresh a singleton in Laravel 5

I have a Provider and in its register method I defined a singleton like this,

$this->app->singleton('my.custom.singleton', function ($app) {
    $config_value = $app->make($this->config('key'));
    return new MyClass($config_value);
});

as you see, I get a config value and put it as a parameter in my class.

In another place of my project, I change the value of config('key') using code:

Config:set('key',$my_changed_value);

and I call a method of MyClass that uses the parameter that I send it to the class in my provider above.

But MyClass not use the new value of config('key'). I think it happens because the singleton has been defined with the default value of config.

I think it will be ok if I could redefine the singleton after assigning new values of config.

Or is there any solution for my issue? Am I wrong? What can I do to use the new value in MyClass?

via Chebli Mohamed