sentinel.go
func IgnoreNetOpError(err error) bool {
	if opErr, ok := err.(*net.OpError); ok {
		return opErr.Err.Error() == "use of closed network connection"
	}
	return false
}
func IgnoreNetOpError(err error) bool {
	if opErr, ok := err.(*net.OpError); ok {
		return opErr.Err.Error() == "use of closed network connection"
	}
	return false
}
// IgnoreNetOpError returns true when the passed error is a net.OpError with
// error "use of closed network connection".