func (e ExperimentalMiddleware) WrapHandler(handler func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error) func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
    return func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
        w.Header().Set("Docker-Experimental", e.experimental)
        return handler(ctx, w, r, vars)
    }