Limiting WordPress Search function : Custom build

This code will only search form woocommerce products. If you want to show any other search result from another post type you can do by simply change post type slug 'product' with you own post type slug 
add_action( 'pre_get_posts', 'wpse223576_search_woocommerce_only' );
function wpse223576_search_woocommerce_only( $query ) {
  if( ! is_admin() && is_search() && $query->is_main_query() ) {
    $query->set( 'post_type', 'product' );
  }
}