Nim. More similar to Go than most languages are to each other, but Nim has (a) more modern features, (b) better compatibility/integration with C libraries, and (c) an amazing macro system. The only thing in Go's favor is the size of its community/ecosystem, which seems to be an accident of timing and most definitely not about inherent quality.
This alone makes Go really unfit for developing system libraries.
If I want something compiled, the killer for Go for me has always been C ABI incompatibility. It's its own island. I'm not saying I wouldn't consider using Go for some things, but that has been a big redflag vs other choices.
"The only thing in Go's favor ..."
The selectivity of a true ideologue.
I've defended Go against detractors who say it's worthless because it has mandatory GC or doesn't have generics (which I do consider a weakness but not a fatal one). There's nothing particularly wrong with Go, but there's not all that much special about it either and it does have flaws. Can you name some other feature that (a) distinguishes Go from Every Other Language and (b) matters? Something that might sway a CEO, as we were discussing? "Goroutines" perhaps? Riiight. That CEO will be really impressed. Don't project your bias onto others.