提交：去掉默认值；

example/lib/main.dart

@@ -29,7 +29,7 @@ class _MyAppState extends State<MyApp> {
     // var result1 = await ClxMapPoiSearch.instance.aroundSearch(31.230378, 121.473658);
     // print("------ result1: $result1");
 
-    var result2 = await ClxMapPoiSearch.instance.aroundSearchAll("北京大学");
+    var result2 = await ClxMapPoiSearch.instance.aroundSearchAll("卫生间", city: "南京",);
     print("------ result2: $result2");
 
   }

lib/clx_map_poi_search.dart

@@ -28,7 +28,7 @@ class ClxMapPoiSearch {
   }
 
   /// 周边搜索
-  Future<PoiResult?> aroundSearchAll(String keywords, { double? latitude = 0, double? longitude = 0, String? city }) {
+  Future<PoiResult?> aroundSearchAll(String keywords, { double? latitude, double? longitude, String? city }) {
     return ClxMapPoiSearchPlatform.instance.aroundSearchAll(keywords, latitude: latitude, longitude: longitude, city: city);
   }
 }