[masklinn]

> Once concurrency is introduced you can now read from the same variable, but another goroutine may have written to the same slice in the meantime. That's why you must protect the read and writes and synchronise them.

But, again, this can easily occur in sequential code as well: you call a function passing it the slice, it mutates the slice internally, it doesn't document that, or maybe the documentation is even wrong, you now hit this issue.