Call an env constant in a middleware file on Laravel

I'm trying to call an .env constant from a Middleware file using Laravel, but I'm only getting Constant expression contains invalid operation.

This is my actual code:

<?php

namespace App\Http\Middleware;

use Illuminate\Foundation\Http\Middleware\VerifyCsrfToken as Middleware;

class VerifyCsrfToken extends Middleware
{
    /**
     * The URIs that should be excluded from CSRF verification.
     *
     * @var array
     */
    protected $except = [
        env("TELEGRAM_BOT_TOKEN") . '/webhook'
    ];
}

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