code: func Fingerprint256(data []byte) string {
  	d := sha256.New()
  	_, _ = d.Write(data) // Never returns an error
  	return base64.RawURLEncoding.EncodeToString(d.Sum(nil))
  }
docs: // Fingerprints
  // Fingerprint256 produces an unpadded, URL-safe Base64-encoded SHA256 digest
  // of the data.