woocommerce-proxy.php

<?php
use Automattic\WooCommerce\Client;

class Custom_Endpoints_Woocommerce_API
{
    protected function get_client() {
        return new Client(
            get_site_url(),
            'woocommerce_consumer_key',
            'woocommerce_consumer_secret',
            [
                'wp_api' => true,
                'version' => 'wc/v1',
            ]
        );
    }

    public function register_woocommerce_routes() {
        register_rest_route( 'customroutes', '/products', array(
            'methods' => 'GET',
            'callback' => array( $this, 'view_products' )
        ));
    }

    public function view_products( WP_REST_Request $request ) {
        $woocommerce = $this->get_client();
        return $woocommerce->get( 'products/categories' );
    }
}

@marekka @fahmifan @DMezhenskyi You can find full document in this link :

https://packagist.org/packages/automattic/woocommerce#3.0.0