const char* AsyncSSLSocket::getSSLCertSigAlgName() const {
  X509* cert = (ssl_ != nullptr) ? SSL_get_certificate(ssl_.get()) : nullptr;
  if (cert) {
    int nid = X509_get_signature_nid(cert);
    return OBJ_nid2ln(nid);
  }
  return nullptr;
}
const char* AsyncSSLSocket::getSSLCertSigAlgName() const {
  X509* cert = (ssl_ != nullptr) ? SSL_get_certificate(ssl_.get()) : nullptr;
  if (cert) {
    int nid = X509_get_signature_nid(cert);
    return OBJ_nid2ln(nid);
  }
  return nullptr;
}