Return authentication exception for Laravel API 5.6

returnException.php

<?php
/**
* Render an exception into an HTTP response.
*
* @param \Illuminate\Http\Request $request
* @param \Exception $exception
* @return \Illuminate\Http\Response
*/
public function render($request, Exception $exception)
{
    // custom exception handler for unauthenticated requests
    if ($exception instanceof AuthenticationException) {
        return response()->json([
            'errors' => [
                'status' => 401,
                'message' => 'Unauthenticated',
            ]
        ], 401);
    }
    // default handler
    return parent::render($request, $exception);
}