Remove woocommerce shipping based on query string in url

I’ve two shipping methods on site, flat_rate and local_pickup. On checkout page i ask user for choice like, Do you want a delivery or pickup? when user select the option,i refresh the page and pass the selection as query string like this: https://www.mysite.com/?shipping=pickup.

So if user select pickup, I want to remove the flat_rate from shipping option. and same when delivery is selected, i want to remove the local_pickup method.

Here is a code i’m using:

/* add shipping variable to query variables */
function add_query_var_for_shipping(){
  add_filter( 'query_vars', 'add_query_vars_filter', 1000 );
}
add_action('init', 'add_query_var_for_shipping', 999);

function add_query_vars_filter( $vars ){
  $vars[] = "shipping";
  return $vars;
}

add_filter( 'woocommerce_package_rates', 'free_shipping_disable_flat_rate' );
function free_shipping_disable_flat_rate( $rates ) {

      if(get_query_var('shipping') == 'pickup'){

        foreach ( $rates as $rate_key => $rate ) {
            if ( 'flat_rate' === $rate->method_id ){
                unset($rates[$rate_key]);
                return $rates;
            }
        }

      }

      if(get_query_var('shipping') == 'delivey'){

        foreach ( $rates as $rate_key => $rate ) {
            if ( 'local_pickup' === $rate->method_id ){
                unset($rates[$rate_key]);
                return $rates;
            }
        }

      }
}

looks like get_query_var(‘shipping’) return null and because of that no shipping method is returned from my code.

Please help. thank you.