render/sse.go
func (es *EventSource) CloseNotify() <-chan bool {
	if cn, ok := es.w.(closeNotifier); ok {
		return cn.CloseNotify()
	}
	return nil
}
func (es *EventSource) CloseNotify() <-chan bool {
	if cn, ok := es.w.(closeNotifier); ok {
		return cn.CloseNotify()
	}
	return nil
}
// CloseNotify return true across the channel when the connection
// in the browser has been severed.