code: func GenSelfTLSFiles(hostname, certPath, keyPath string) (fingerprint string, err error) {
  	cert, key, err := GenSelfTLS(hostname)
  	if err != nil {
  		return "", err
  	}
  	sig, err := CertFingerprint(cert)
  	if err != nil {
  		return "", fmt.Errorf("could not get SHA-256 fingerprint of certificate: %v", err)
  	}
  	if err := wkfs.WriteFile(certPath, cert, 0666); err != nil {
  		return "", fmt.Errorf("failed to write self-signed TLS cert: %v", err)
  	}
  	if err := wkfs.WriteFile(keyPath, key, 0600); err != nil {
  		return "", fmt.Errorf("failed to write self-signed TLS key: %v", err)
  	}
  	return sig, nil
  }
docs: // GenSelfTLSFiles generates a self-signed certificate and key for hostname,
  // and writes them to the given paths. If it succeeds it also returns
  // the SHA256 prefix of the new cert.