how can I fix Django cannot unpack non-iterable int object?

I am kind of a beginner and I'm doing an ecommerce web-site now and in views I have get_object_404 and parameters to go with it but I keep getting cannot unpack non-iterable int object with an id parameter. I searched the topic and mostly found same problem with pk and it didn't work with id(or maybe I couldn't make it work who knows). here's the code: views.py:

from django.shortcuts import render, get_object_or_404
from .models import *
from cart.forms import CartAddProductForm

def product_list(request, category_slug=None):
    category = None
    categories = Category.objects.all()
    products = Product.objects.filter(available=True)
    if category_slug:
        category = get_object_or_404(Category, slug=category_slug)
        products = products.filter(category=category)
    context = {
        'categories': categories,
        'category': category,
        'products': products,
    }
    return render(request, 'onlineshop/product/list.html', context)


def product_detail(request, id, slug):
    product = get_object_or_404(Product, id, slug=slug)
    cart_product_form = CartAddProductForm()
    context = {
        'product': product,
        'cart_product_form':cart_product_form,
    }
    return render(request, 'onlineshop/product/detail.html')

urls.py:

from django.urls import path
from . import views

app_name = 'onlineshop'

urlpatterns = [
    path('', views.product_list, name='product_list'),
    path('<slug:category_slug>/', views.product_list,
         name='product_list_by_category'),

    path('<int:id>/<slug:slug>/', views.product_detail, name='product_detail')
]

models.py:

from django.db import models
from django.urls import reverse


class Category(models.Model):
    name = models.CharField(max_length=200, db_index=True)
    slug = models.SlugField(max_length=200, unique=True)

    class Meta:
        ordering = ('name',)
        verbose_name = 'category'
        verbose_name_plural = 'categories'

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse('onlineshop:product_list_by_category', args=[self.slug])


class Product(models.Model):
    category = models.ForeignKey(
        Category, related_name='product', on_delete=models.CASCADE)
    name = models.CharField(max_length=200, db_index=True)
    slug = models.SlugField(max_length=200, db_index=True)
    image = models.ImageField(upload_to='products/%Y/%m/%d', blank=True)
    description = models.TextField(blank=True)
    price = models.DecimalField(max_digits=10, decimal_places=2)
    available = models.BooleanField(default=True)
    created = models.DateTimeField(auto_now_add=True)
    updated = models.DateTimeField(auto_now=True)

    class Meta:
        ordering = ('name',)
        index_together = (('id', 'slug'))

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse('onlineshop:product_detail', args=[self.id, self.slug])