Wait, what? Do you have any references for that? My impression was that Go creates new threads for new Goroutines when the current ones are blocked. Is that not how it works?
The Go runtime creates new threads to run goroutines when a thread is blocked making a syscall. The net package avoids having too many threads blocking on syscalls by using epoll/kqueue etc. for socket I/O.
The goroutine is a user-thread, Go can create as many threads as there are cores and schedules user-threads inside these threads without the programmer managing that, you just create goroutines. When a goroutine "blocks" it schedules out from the thread and another can replace it.