code: func (s *Set) checkSHA256(certificate *x509.Certificate) bool {
  	actualHash := sha256.Sum256(certificate.RawSubjectPublicKeyInfo)
  	actualHashHex := strings.ToLower(hex.EncodeToString(actualHash[:]))
  	return s.sha256Hashes[actualHashHex]
  }
docs: // checkSHA256 returns true if the certificate's "sha256" hash is pinned in the Set