Untitled

インターフェース	io.Reader	io.Writer	io.Seeker	io.Closer
io.ReadWriter	◯	◯
io.ReadSeeker	◯		◯
io.ReadCloser	◯			◯
io.WriteSeeker		◯	◯
io.WriteCloser		◯		◯
io.ReadWriteSeeker	◯	◯	◯
io.ReadWriteCloser	◯	◯		◯