NewReader returns a new hash Reader which computes the MD5 sum and SHA256 sum (if set) of the provided io.Reader at EOF.

BadDigest - Content-MD5 you specified did not match what we received.

Reader writes what it reads from an io.Reader to an MD5 and SHA256 hash.Hash.

SHA256Mismatch - when content sha256 does not match with what was sent from client.