Autoloading with composer doesn't work when using psr-4

Question

I have an issue running a function when use psr-4 autoloading.

When i declare directly which files should be in autoloading everything works fine. When i switch to psr-4 then i get log that the function is undefined.

src/cli.php:

namespace Php\Project1\Cli;

function run()
{
  ...
}

bin/brain-games:

#!/usr/bin/env php

<?php

$autoloadPath1 = __DIR__ . '/../../../autoload.php';
$autoloadPath2 = __DIR__ . '/../vendor/autoload.php';

if (file_exists($autoloadPath1)) {
    require_once $autoloadPath1;
} else {
    require_once $autoloadPath2;
}

use function Php\Project1\Cli\run;
run();

composer.json:

"autoload": {
      "psr-4": {
        "Php\\Project1\\": "src/"
      }
  },

The error that i get is:

PHP Fatal error:  Uncaught Error: Call to undefined function Php\Project1\Cli\run() in /home/arkadiy/php-project1/bin/brain-games:15
Stack trace:
#0 {main}
  thrown in /home/arkadiy/php-project1/bin/brain-games on line 15