item_fee - 获得1688商品快递费用
测试网址：注册送淘宝/天猫商品详情接口
Result Object: --------------------------------------- { "item": { "num_iid": "534409796654", "area_id": "2274", "location": null, "shipping_to": "新余", "express_fee": "", "ems_fee": "", "post_fee": "", "freightTemplateId": null, "price": null, "beginAmount": null, "unitWeight": null, "memberId": null }, "error": "data error,no cache", "reason": "data error,no cache", "error_code": "5000", "cache": 0, "api_info": "today: max:", "execution_time": 0.2, "server_time": "Beijing/2020-07-05 09:50:01", "call_args": { "num_iid": "534409796654", "area_id": "2274" }, "api_type": "1688", "translate_language": "zh-CN", "translate_engine": "google_cn", "request_id": "15f0131c8deff8" }