What are you referring to here? Go's current slice implementation could only possibly introduce unsoundness via data races. Even there, I think you might actually need to muck around with an interface value rather than a slice to demonstrate unsoundness of the type system (rather than just memory corruption or unsafe memory access).

Typescript's type system is just deliberately unsound by design (for defensible reasons). It's a whole nother level of unsoundness in comparison to Go.