Because go is always multithreaded. You literally cannot do certain system level things in Go. For instance trying to "setns" to a mount namespace will yield EI

Because go is always multithreaded. You literally cannot do certain system level things in Go. For instance trying to "setns" to a mount namespace will yield EINVAL from the kernel in all cases with Go. In fact, all namespace related operations are really annoying to do from Go because the runtime is always multithreaded and you have no control over the threading except for locking the active goroutine to its currently assigned thread. This also makes that thread unusable for any new goroutine (even goroutines that are spawned from code running in that thread), which has the side-effect that the new goroutine will always be in the original namespace context.