code: func (a *Account) GetPrivateKey() crypto.PrivateKey {
  	privateKey, err := x509.ParsePKCS1PrivateKey(a.PrivateKey)
  	if err != nil {
  		log.WithoutContext().WithField(log.ProviderName, "acme").
  			Errorf("Cannot unmarshal private key %+v: %v", a.PrivateKey, err)
  		return nil
  	}
  
  	return privateKey
  }
docs: // GetPrivateKey returns private key