Don't do os.Exit()

[gelin]

Current implementation calls logger.Fatalf() (and os.Exit() inside) when it's not possible to create objects.

For example:

func (node *defaultNode) NewPublisherWithCallbacks(topic string, msgType MessageType, connectCallback, disconnectCallback func(SingleSubscriberPublisher)) Publisher {
	//...
		_, err := callRosApi(node.masterUri, "registerPublisher",
			node.qualifiedName,
			name, msgType.Name(),
			node.xmlrpcUri)
		if err != nil {
			logger.Fatalf("Failed to call registerPublisher(): %s", err)
		}
	//...
}

The better is to return (Publisher, error) in this case and involve typical Go error handling mechanics than unconditionally die.

I'm building a service where ROS node can be started later, some functionality of it doesn't depend on ROS. But I cannot start when ROS master is not available because of os.Exit() in the rosgo.