There's a blub on "why Go?" on the website if you're interested.
https://gvisor.dev/docs/architecture_guide/
> gVisor is written in Go in order to avoid security pitfalls that can plague kernels. With Go, there are strong types, built-in bounds checks, no uninitialized variables, no use-after-free, no stack overflow, and a built-in race detector. (The use of Go has its challenges too, and isn’t free.)