Laravel 5 - Validation

I am confuse how can I validate a user's username if I am updating it. Here's the scenario, if I click a specific user in list of users page it will redirect into a page which has a form with user's data in the form. Now, I have:

public function updateUser(Request $request){

   $this->validate($request, [
      'username' => 'required|unique:users',
      'name' => 'required|max:255'
   ]);

}

I know the part where 'username' => 'required|unique:users' is checking if the username exists in the users table, but what if I dont want to change/update the username, and I just want to update the other field, then it says that the username is already exists. How can I validate it in a right way.

Need help guys. This can also help others for this kind of problem.

via Chebli Mohamed