func permissibleCloseCode(err error) bool {
	return websocket.IsCloseError(err,
		websocket.CloseNormalClosure,     // websocket error code 1000
		websocket.CloseAbnormalClosure,   // websocket error code 1006
		websocket.CloseGoingAway,         // websocket error code 1001
		websocket.CloseInternalServerErr) // websocket error code 1011
}
func permissibleCloseCode(err error) bool {
	return websocket.IsCloseError(err,
		websocket.CloseNormalClosure,     // websocket error code 1000
		websocket.CloseAbnormalClosure,   // websocket error code 1006
		websocket.CloseGoingAway,         // websocket error code 1001
		websocket.CloseInternalServerErr) // websocket error code 1011
}
// See https://github.com/gorilla/websocket/blob/87f6f6a22ebfbc3f89b9ccdc7fddd1b914c095f9/conn.go#L650