STM isn't really used in Go like it is in Haskell.

Here's the example from a Go STM package that's based on Haskell STM. It has gotchas that you won't encounter in Haskell though, due to the nature of these languages.

https://github.com/anacrolix/stm/blob/master/cmd/santa-examp...

For the equivalent Haskell, check out the link at the top of the file.