Cannot add or update a child row 'user_id' - php

Question

When I submit my form I can see in the error that all my values are passed except 'user_id':
('insert into `products` (`title`, `body`, `address`, `condition`, `quantity`, `price`, `bid_price`, `img_1`, `updated_at`, `created_at`)
But there's missing 'user_id', why ? This is my Product.php
protected $fillable = ['slug', 'title', 'body', 'user_id', 'price', 'bid_price', 'address', 'condition', 'quantity', 'img_1', 'img_2', 'img_3', 'img_4', 'views'];
The function in controller:
public function storeAuction(AuctionSubmitRequest $request)
{
$product = Product::create($request->all());
Auth::user()->product()->save($product);
$request->file('img_1')->move(public_path('images'), $request->file('img_1')->getClientOriginalName());
$data = $request->except(['img_1']);
$data['img_1'] = public_path('images') . '/' . $request->file('img_1')->getClientOriginalName();
$product->create($data);
return redirect('/');
}
My form:
<form id="tryitForm" class="form-horizontal" method="POST" action="/paskelbti-nauja-aukciona" enctype="multipart/form-data">
{!! csrf_field() !!}
<div class="form-group">
<label class="col-md-3 control-label">Prekės pavadinimas</label>
<div class="col-md-4">
<input type="text" class="form-control" name="title" />
</div>
</div>
<div class="form-group">
<label class="col-md-3 control-label">Prekės aprašymas</label>
<div class="col-md-4">
<textarea name="body" class="form-control"></textarea>
</div>
</div>
<div class="form-group">
<label class="col-md-3 control-label">Adresas</label>
<div class="col-md-6">
<input type="text" class="form-control" name="address" />
</div>
</div>
<div class="form-group">
<label class="col-md-3 control-label">Pristatymas</label>
<div class="col-md-6">
<div class="radio">
<label><input type="radio" name="dispatch" value="kurjeris" /> Kurjeriu</label>
</div>
<div class="radio">
<label><input type="radio" name="dispatch" value="pastas" /> Paštu</label>
</div>
<div class="radio">
<label><input type="radio" name="dispatch" value="kita" /> Kita (parašysiu "prekės aprašyme")</label>
</div>
</div>
</div>
<div class="form-group">
<label class="col-md-3 control-label">Prekės būklė</label>
<div class="col-md-6">
<div class="radio">
<label><input type="radio" name="condition" /> Nauja</label>
</div>
<div class="radio">
<label><input type="radio" name="condition" /> Labai gera</label>
</div>
<div class="radio">
<label><input type="radio" name="condition" /> Gera</label>
</div>
<div class="radio">
<label><input type="radio" name="condition" /> Panaudota</label>
</div>
</div>
</div>
<div class="form-group">
<label class="col-md-3 control-label">Barkodas (jei turite)</label>
<div class="col-md-4">
<input class="form-control" name="barcode" type="number" min="0" />
</div>
</div>
<div class="form-group">
<label class="col-md-3 control-label">Prekių kiekis</label>
<div class="col-md-2">
<input class="form-control" name="quantity" type="number" min="1" />
</div>
</div>
<div class="form-group">
<label class="col-md-3 control-label">Prekės nuotraukos</label>
<div class="col-md-6">
<input type="file" class="form-control" name="img_1" /><br>
<input type="file" class="form-control" name="img_2" /><br>
<input type="file" class="form-control" name="img_3" /><br>
<input type="file" class="form-control" name="img_4" />
</div>
</div>
<div class="form-group">
<label class="col-md-3 control-label">Prekės kaina</label>
<div class="col-md-2">
<input class="form-control" name="price" type="number" step="0.01" min="0.01" />
</div>
</div>
<div class="form-group">
<label class="col-md-3 control-label">Minimali siūlymo suma</label>
<div class="col-md-2">
<input class="form-control" name="bid_price" type="number" step="0.01" min="0.01" />
</div>
</div>
<div class="form-group">
<div class="col-md-offset-3 col-md-8">
<button type="submit" class="btn btn-primary">Pradėti aukcioną</button>
</div>
</div>
</form>

Answer 1

You may try something like the following.
public function storeAuction(AuctionSubmitRequest $request)
{
$request->file('img_1')->move(public_path('images'), $request->file('img_1')->getClientOriginalName());
// first create the related model, do not save or create
// because you will get a 'Cannot add or update a child row'
$product = new Product();
$product->property1 = $request->get('property1');
$product->property2 = $request->get('property2');
// ...
$product->img_1 = public_path('images') . '/' . $request->file('img_1')->getClientOriginalName();
// here you save a product associated to the user.
Auth::user()->product()->save($product);
return redirect('/');
}