Lumen Validate Route Parameters

Route.php

$app->get('member/{member_id}','MemberController@show');

---------
MemberController.php

public function show(Request $request , $member_id)
{
    $request['member_id'] = $member_id;
    $this->validate($request , ['member_id'=>'required|exists:members,id']);
    
    // do something else
}