shareit/app/Mail/UserWaiting.php

<?php

namespace App\Mail;

use \App\Item;
use Illuminate\Bus\Queueable;
use Illuminate\Mail\Mailable;
use Illuminate\Queue\SerializesModels;
use Illuminate\Contracts\Queue\ShouldQueue;

class UserWaiting extends Mailable
{
    public $item;
    public $waitingUser;
    public $userWithItem; 
    use Queueable, SerializesModels;

    /**
     * Create a new message instance.
     *
     * @return void
     */
    public function __construct($waitingUser, $userWithItem, Item $item)
    {
        $this->item = $item;
        $this->waitingUser = $waitingUser;
        $this->userWithItem = $userWithItem;
    }

    /**
     * Build the message.
     *
     * @return $this
     */
    public function build()
    {
        return $this->subject($this->waitingUser . ' wants to use ' . $this->item->name)
            ->markdown('emails.userWaiting');
    }
}