SearchDelegate With Http

I try to using searchdelgit with future list from JSON, when. But I got this error:

formatException :Unexpected character (at line 2 , character1)

altho I already use the same code without search page and it works perfectly

any idea guys

 @override
  Widget buildResults(BuildContext context) {
    // show some result based on the selection
    if (query.length < 3) {
      return Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Center(
            child: Text(
              "Search term must be longer than two letters.",
            ),
          )
        ],
      );
    }
    return FutureBuilder(
      future: _fetchProductSearch(query),
      builder: (context, AsyncSnapshot<List<Products>> snapshot) {
        if (!snapshot.hasData) {
          return Text(snapshot.error.toString());
        } else if (snapshot.data.length == 0) {
          return Column(
            children: <Widget>[
              Text(
                "No Results Found.",
              ),
            ],
          );
        } else {
          var results = snapshot.data;
          return ListView.builder(
            itemCount: results.length,
            itemBuilder: (context, index) {
              var result = results[index];
              return ListTile(
                title: Text(result.artitle),
              );
            },
          );
        }
      },
    );
  }

formatException :Unexpected character (at line 2 , character1)