要使用stock_status参数，在调用API时需要将其作为查询参数添加到URL末尾。以下是一个示例：

import 'dart:convert';
import 'package:http/http.dart' as http;

Future> getProductsWithStockStatus(String stockStatus) async {
  final url =
      "https://example.com/wp-json/wc/v3/products?consumer_key=YOUR_CONSUMER_KEY&consumer_secret=YOUR_CONSUMER_SECRET&stock_status=$stockStatus";
  
  final response = await http.get(Uri.parse(url));
  
  if (response.statusCode == 200) {
    final products = jsonDecode(response.body) as List;
    return products;
  } else {
    throw Exception('Failed to load products');
  }
}

在上面的示例中，我们使用http包发出GET请求，并将stock_status添加到URL的末尾。注意替换url、YOUR_CONSUMER_KEY和YOUR_CONSUMER_SECRET。