AddVersion permits a framework to register its version, assuming it's one of the officially supported frameworks.
GetHostname returns the hostname of the current device. Caches the hostname between calls to ensure this is performant. Returns a blank string in case that the hostname cannot be identified.
RuntimeVersions define the various versions of Go and any framework that may be in use. As a user of the notifier you're unlikely to need to modify this struct. As such, the authors reserve the right to introduce breaking changes to the properties in this struct. In particular the framework versions are liable to change in new versions of the notifier in minor/patch versions.
GetRuntimeVersions retrieves the recorded runtime versions in a goroutine-safe manner.