goaのDSL内でFiles()を記述したとき、genとexampleの結果で食い違いが出てエラーになる

var _ = Service("bottle", func() {
    Files("/index.json", "/www/data/index.json", func() {
        Description("Serve home page.")
        Docs(func() {
            Description("Additional documentation")
            URL("https://goa.design")
        })
    }) 
})

#...etc
bottleServer = bottlesvr.New(bottleEndpoints, mux, dec, enc, eh, nil)

func New(
	e *health.Endpoints,
	mux goahttp.Muxer,
	decoder func(*http.Request) goahttp.Decoder,
	encoder func(context.Context, http.ResponseWriter) goahttp.Encoder,
	errhandler func(context.Context, http.ResponseWriter, error),
	formatter func(ctx context.Context, err error) goahttp.Statuser,
	fileSystemGenHTTPIndexJSON http.FileSystem,
) *Server {