set_headers.go
func NewSetHeadersHandler(h http.Handler, headers map[string]string) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		for header, value := range headers {
			w.Header().Set(header, value)
		}
		h.ServeHTTP(w, r)
	})
}
func NewSetHeadersHandler(h http.Handler, headers map[string]string) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		for header, value := range headers {
			w.Header().Set(header, value)
		}
		h.ServeHTTP(w, r)
	})
}
// NewSetHeadersHandler sets provied headers on HTTP response.