> Or a third option can be to write your hot loops in one such language; and continue using Go for everything else. Problem solved.

Or use Go and write ugly code for those hot loops instead of introducing another language and build system. Then you can still enjoy nicety of GC in other parts of your code.

I can see that being an option in a small team that works closely with one another and wants to keep things simple.

Though it is my personal opinion that forcing a GC-based language to do a task best suited for manual memory management is like swimming against the tide. It’s doable but more challenging than it ought to be. I might even appreciate the challenge but the next person maintaining the code might not.