HealthCheckReconnectUnit: 200 * time.Millisecond,
		HealthCheckTimeout:       time.Second,
	}
	if err != nil {
		clnt.lastErr = err
		clnt.lastErrTime = time.Now()
	}

	if clnt.HealthCheckFn != nil {
		// make connection pre-emptively.
		go clnt.HealthCheckFn()
	}
	return clnt
}

// IsOnline returns whether the client is likely to be online.
func (c *Client) IsOnline() bool {