[Vuejs]-How to solve 500 (Internal Server Error) SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'user_id' cannot be null?

sry i wrote wrong answer, because i could not write comment

you using wrong class.
try import this

use Illuminate\Support\Facades\Auth;

Try this:

$user = Auth::user();

$comment = $post->comments()->create([
    'body' => $request->body,
    'user_id' => $user->id
]);