How to update data in database using import excel

how to update data in database with import excel. i am using laravel 5.7 and maatwebsite 3.1

this is my controller :

public function import()
{
   $data = Excel::toArray(new ProdukImport, request()->file('file')); 
   if ($data) {
       DB::table('produk')
            ->where('id_produk', $data['id'])
            ->update($data);
   }
}

This is my Import Class:

<?php

 namespace App\Imports;

 use App\Produk;
 use Maatwebsite\Excel\Concerns\ToModel;
 use Maatwebsite\Excel\Concerns\WithHeadingRow;


 class ProdukImport implements ToModel, WithHeadingRow
 {
    /**
     * @param array $row
     *
     * @return \Illuminate\Database\Eloquent\Model|null
     */
    public function model(array $row)
    {
       return new Produk([
          'id_produk' => $row['id'],
          'nama_produk' => $row['produk'],
          'harga_jual' => $row['harga']
       ]);
     }
  }

via Chebli Mohamed