Error: Method Store does not exist. When trying to store a file. Laravel 5.3

• Laravel Version 5.3
• PHP Version: 5.6
• Database Driver & Version: MySql

When i try to use the store method from the documentation:
https://laravel.com/docs/5.3/filesystem#file-uploads i got error: Method store does not exist.
Also i've wached this video in laracasts, writing the exact same code: https://laracasts.com/series/whats-new-in-laravel-5-3/episodes/12 and the result is the same.
This is my code:

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use Illuminate\Support\Facades\Validator;
use Illuminate\Support\Facades\Storage;
use Illuminate\Support\Facades\File;
use App\Http\Requests;

class UserController extends Controller {

    protected $validationRules = [
        'avatar' => 'mimes:jpg,png,gif,jpeg'
    ];
    

    public function store(Request $request){

      $validator = Validator::make($request->all(), $this->validationRules);
      if($validator->passes()){
          $path = $request->file('avatar')->store('avatars'); // here is the problem
          dd($path);
      }else{
          dd($validator->messages());
      }
    }

Route::post('/user/store', 'UserController@store');