I've been a professional C, Perl, PHP and Python developer.
I'm an ex-sysadmin from the late 20th century.
These days I do more Javascript and CSS and whatnot, and promote UX and accessibility.
There are many people interested to track those stats and I don't see the problem to check who unfollowed me, let's say: curiosity.
You suggested another use case for example :D
Anyway, it was a nice exercise to learn Go with Twitter's APIs. :)
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We're a place where coders share, stay up-to-date and grow their careers.
Unless 90% of your followers all disappear at the same time, why do you care if someone unfollows you?
Maybe you care because you've changed your style recently and you want to know what kind of people like it and what kind of people don't. I guess.
Otherwise...? People follow and unfollow others all the time. Let them be.
There are many people interested to track those stats and I don't see the problem to check who unfollowed me, let's say: curiosity.
You suggested another use case for example :D
Anyway, it was a nice exercise to learn Go with Twitter's APIs. :)