Package hmac implements the Keyed-Hash Message Authentication Code (HMAC) as
defined in U.S. Federal Information Processing Standards Publication 198. An
HMAC is a cryptographic hash that uses a key to sign a message. The receiver
verifies the hash by recomputing it using the same key.

• func New(h func() hash.Hash, key []byte) hash.Hash

Equal compares two MACs for equality without leaking timing information.

New returns a new HMAC hash using the given hash.Hash type and key. Note that
unlike other hash implementations in the standard library, the returned Hash
does not implement encoding.BinaryMarshaler or encoding.BinaryUnmarshaler.