If I understand correctly, you still need guarding locks for this if reading and writing at same time, or have multiple writers. Isn't this the same as for the native map?
It's not clear from the code; the author probably should clarify what "Goroutine safety" means - for reads or for read/write? Your correct about the approach for native maps.
EDIT: The package description punctuation is hard to grasp, but upon a second read, "Goroutine Safety." might be intended as a headline for the next line, which starts with "No." Read that way, your understanding sounds correct.
EDIT: The package description punctuation is hard to grasp, but upon a second read, "Goroutine Safety." might be intended as a headline for the next line, which starts with "No." Read that way, your understanding sounds correct.