[hash.Hash] type and key. func New[H hash.Hash](h func() H, key []byte) *HMAC { hm := &HMAC{keyLen: len(key)} hm.outer = h() hm.inner = h() unique := true func() { defer func() { // The comparison might panic if the underlying types are not comparable. _ = recover() }() if hm.outer == hm.inner { unique = false } }() if !unique { panic("crypto/hmac: hash generation function does not produce unique values") } blocksize := hm.inner.BlockSize() hm.ipad = make([]byte, blocksize) hm.opad = make([]byte, blocksize)...