getTokenForRequest always returns null in Laravel 5.2.31

I am working on API in Laravel. My route is below.

Route::group(['prefix' => 'api/v1', 'middleware' => 'auth.api'], function () {
    Route::get('/DownloadMedia/{MediaID}', 'MediaController@DownloadMedia');
});

In below file

\vendor\laravel\framework\src\Illuminate\Auth\TokenGuard.php

Method: getTokenForRequest() always returns Token value = null

when I started the debugging and printed the value of dd($this->request);

I get below values.

Here is problem is why getTokenForRequest() is always null?

bearerToken() and $this->request->input($this->inputKey) and $this->request->getPassword() all are null

Can you explain why this is null?

My Url is below

http://ift.tt/1TLmdxo

via Chebli Mohamed