WooCommerce Package Rates (Looping 2 Times) Creates Multiplied Rate Costs - woocommerce

Question

Using the filter, woocommerce_package_rates, it works at first, but upon loading the checkout page, it seems to load this filter multiple times.
Example.
If the cost of shipping is, $20. I need to multiply this by 2, which should be $40.
But it will loop again, and it will become $80.
When I first load the checkout, it shows the right price, but after 2 seconds, it adjusts it again to $80.
Not sure what to do here, or how to handle this.
add_filter( 'woocommerce_package_rates', 'woocommerce_shipping_rates', 10, 2);
function woocommerce_shipping_rates($rates, $package) {
$multiplier = 2;
foreach ( $rates as $rate_key => $rate ){
if( 'canada_post' === $rate->method_id ) {
$has_taxes = false;
// Set the new cost
//echo "CALC:". $rate->cost ." * ". $multiplier ;
$rates[$rate_key]->cost = $rate->cost * $multiplier ;
// Taxes rate cost (if enabled)
foreach ($rates[$rate_key]->taxes as $key => $tax){
if( $tax > 0 ){
// New tax calculated cost
$taxes[$key] = $tax * $multiplier ;
$has_taxes = true;
}
}
// Set new taxes cost
if( $has_taxes )
$rates[$rate_key]->taxes = $taxes;
}
}
return $rates;
}