code: func NewDNSProviderServiceAccount(saFile string) (*DNSProvider, error) {
  	if saFile == "" {
  		return nil, fmt.Errorf("googlecloud: Service Account file missing")
  	}
  
  	saKey, err := ioutil.ReadFile(saFile)
  	if err != nil {
  		return nil, fmt.Errorf("googlecloud: unable to read Service Account file: %v", err)
  	}
  
  	return NewDNSProviderServiceAccountKey(saKey)
  }
docs: // NewDNSProviderServiceAccount uses the supplied service account JSON file
  // to return a DNSProvider instance configured for Google Cloud DNS.