It looks kind of interesting, but for me these are the bar to beat, "modern" without GUI tooling, automation and reporting capabilities just isn't interesting.

https://jmeter.apache.org/

https://www.radview.com/

https://www.smartmeter.io/

https://www.loadview-testing.com/

https://smartbear.com/product/ready-api/loadui/overview/

Another more basic (like OP's) but still popular one (>13k GitHub stars) and also written in Go is Vegeta: https://github.com/tsenart/vegeta

I like the simplicity and the fact that it's free and feels frills free compared to the expensive solutions posted below is refreshing.

Cassowary is the name for a well-known layout constraint solving system. Taken!

And also of a terrifying large Australian bird that should be treated with extreme caution.