Thanks! Maybe I will write an article. If I understand your question correctly, in this case db-01 and db-02 are instances that have corresponding IP addresses, which were assigned by the hosting provider (DigitalOcean and Linode in those examples) during the creation process.

I built something similar called Overcast using Node.js and native SSH. Beyond running commands and script files on multiple servers, it includes API support for a number of different cloud providers. I haven't tried using it on hundreds of servers though, I'd be curious to see how it performs — probably not as well as your Go example.