It's available as part of the cockroach binary (https://www.cockroachlabs.com/docs/releases/v2.1.0-beta.2018...) as a subcommand. And an external contributor has made a more standalone version at https://github.com/lopezator/sqlfmt.

I searched around and found https://github.com/jackc/sqlfmt, which is an older open source project also called sqlfmt, also written in Go. I don't know anything about how they compare.