There are functions in log.go that emit message to stdout (thinking about it, I need to send warnings and above to stderr).
The function err(), in addition to sending a message to stdout, also causes an exit of the process. But it does so only if ExitOnError is turned on; which is on by default, and can be turned off by setting environment variable EXIT_ON_ERROR=true.
I have converted that Gist into a standalone Git repo, and hope to update it to add more improvements (like the stderr change, above) to showcase how to leverage GoLang for scripting.