Please go through Go Plugin User Guide before using Go plugin
Please follow link for package material extension point details.
Go bundles a Yum repository poller extension, along with the server. You can find out more details about it here.
See this for details about the task extension point. Go does not have a bundled task extension. You can see Curl task extension for reference.
See this for details about the notification extension point. Go does not have a bundled notification extension. You can see Email notification extension for reference.