opts.go
func GoogleServiceAccountCredentialsFile(path string) Option {
	return func(sh *StackdriverHook) error {
		buf, err := ioutil.ReadFile(path)
		if err != nil {
			return err
		}

		return GoogleServiceAccountCredentialsJSON(buf)(sh)
	}
}
func GoogleServiceAccountCredentialsFile(path string) Option {
	return func(sh *StackdriverHook) error {
		buf, err := ioutil.ReadFile(path)
		if err != nil {
			return err
		}

		return GoogleServiceAccountCredentialsJSON(buf)(sh)
	}
}
// GoogleServiceAccountCredentialsFile is an option that loads Google Service
// Account credentials for use with the StackdriverHook from the specified
// file.
//
// Google Service Account credentials can be downloaded from the Google Cloud
// console: https://console.cloud.google.com/iam-admin/serviceaccounts/