An `io.Reader` returns `n > 0` and `err == io.EOF` in the same call. What should the call…

An `io.Reader` returns `n > 0` and `err == io.EOF` in the same call. What should the caller do?

1. Process the first `n` bytes, then handle the EOF.
2. Discard the bytes because every non-nil error invalidates `n`.
3. Retry the same read until it returns the bytes with a nil error.