Variable not defined in EJS template

<input class="form-control" type="text" name="name" value="<%= product.name %>" placeholder="name"> product is not defined

This is my route file:

const express = require('express')
const router = express.Router()
const imageMimeTypes = ['image/jpeg', 'image/png', 'images/gif']

//GET product model
var Product = require('../models/product')

//GET Category model
var Category = require('../models/category')

//GET All product Page
router.get('/', async(req, res) => {
    let query = Product.find()
    if (req.query.name != null && req.query.name != '') {
        query = query.regex('name', new RegExp(req.query.name, 'i'))
    }
    try {
        const products = await query.exec()
        res.render('admin/products', {
            products: products,
            searchOptions: req.query
        })
    } catch {
        res.redirect('/')
    }
});

//GET category page
router.get('/add-product', async(req, res) => {
    res.render('admin/add_product')
});

//POST Add page
router.post('/', async(req, res) => {

    const product = new Product({
        name: req.body.name,
        category: req.body.category,
        price: req.body.price,
        shopName: req.body.shopName,
        district: req.body.district,
        productCount: req.body.productCount,
        description: req.body.description
    })
    saveCover(product, req.body.cover)

    try {
        const newProduct = await product.save()
            // res.redirect(`products/${newProduct.id}`)
        res.redirect(`products`)
    } catch {
        renderNewPage(res, products, true)
    }
});

async function renderNewPage(res, products, hasError = false) {
    try {
        const categories = await Category.find({})
        const params = {
            categories: categories,
            product: product
        }
        if (hasError) params.errorMessage = 'Error Adding Product'
        res.render('admin/add_product', params)
    } catch {
        res.redirect('/products')
    }
}

function saveCover(book, coverEncoded) {
    if (coverEncoded == null) return
    const cover = JSON.parse(coverEncoded)
    if (cover != null && imageMimeTypes.includes(cover.type)) {
        product.productImage = new Buffer.from(cover.data, 'base64')
        product.productImageType = cover.type
    }
}


module.exports = router;