Recreate listener if error is occured

[clyang82]

recreate the listener when the notify is nil or there is an error for Ping()
here is the document for notify is nil

A notification channel will remain open until Unlisten is called, though connection loss might
result in some notifications being lost. To solve this problem, Listener sends
a nil pointer over the Notify channel any time the connection is re-established
following a connection loss. The application can get information about the
state of the underlying connection by setting an event callback in the call to
NewListener.

[skeeey]

how about new the listener in the goroutine waitForNotification? we can maintain the listener in one place, may like

func waitForNotification() {
   listener := newListener(ctx, f.config, channel)
   for {
     		// ...	
		// recreate the listener
		listener = newListener(ctx, dbConfig, channel)
        }
    }
}