unable to get all users from laravel 5.3 - laravel

Question

my controller is RegisterController which is in controller in auth folder
<?php
namespace App\Http\Controllers\Auth;
use Illuminate\Http\Request;
use App\User;
use App\Http\Controllers\Controller;
use Illuminate\Support\Facades\Validator;
use Illuminate\Foundation\Auth\RegistersUsers;
class RegisterController extends Controller
{
/*
|--------------------------------------------------------------------------
| Register Controller
|--------------------------------------------------------------------------
|
| This controller handles the registration of new users as well as their
| validation and creation. By default this controller uses a trait to
| provide this functionality without requiring any additional code.
|
*/
use RegistersUsers;
/**
* Where to redirect users after registration.
*
* #var string
*/
protected $redirectTo = '/home';
/**
* Create a new controller instance.
*
* #return void
*/
public function __construct()
{
$this->middleware('guest');
}
/**
* Get a validator for an incoming registration request.
*
* #param array $data
* #return \Illuminate\Contracts\Validation\Validator
*/
protected function validator(array $data)
{
return Validator::make($data, [
'name' => 'required|max:255',
'email' => 'required|email|max:255|unique:users',
'password' => 'required|min:6|confirmed',
]);
}
/**
* Create a new user instance after a valid registration.
*
* #param array $data
* #return User
*/
protected function create(Request $request)
{
$this->validate($request, [
'first_name' => 'required|max:255',
'middle_name' => 'string|max:255',
'last_name' => 'required|max:255',
'email' => 'required|max:255|unique:users',
'password' => 'required|min:6|',
'user_status' => 'required|max:255',
'user_role' => 'required|max:255',
'user_type' => 'required|max:255',
'phone' => 'required|max:255',
'address' => 'required|max:255',
]);
return User::create([
'first_name' => $request['first_name'],
'middle_name' => $request['middle_name'],
'last_name' => $request['last_name'],
'email' => $request['email'],
'password' => bcrypt($request['password']),
'user_status' => $request['user_status'],
'user_role' =>$request['user_role'],
'user_type' =>$request['user_type'],
'phone' =>$request['phone'],
'address' =>$request['address'],
]);
}
public function index(){
return User::all();
}
}
And my api.php file in routes folder is
Route::get('/users','Auth\RegisterController#index')->middleware('auth');
I want to all data from user table which code is in Auth\Regitercontroller in index function this route returns
{
"error":"unauthenticated",
}
so i want aall user from table user and if i remove middleware->('auth:api') from routes then i got all users but i want middleware in routes for security reason so help me.Thank You