*pool.RW implements io.Closer, so when one is used directly as an
http.Request body the transport closes it after each attempt. A retry
which then seeks and re-reads the RW would index the freed pages and
panic with "index out of range" in readPage.
Read, Write, ReadFrom, WriteTo and Seek now return ErrClosed (which
wraps io/fs.ErrClosed) after Close, and Close is safe to call more
than once.
Nick Craig-Wood
55fa9b6ab2