// Acknowledge method acknowledges an alert at OpsGenie.
func (cli *OpsGenieAlertClient) Acknowledge(req alerts.AcknowledgeAlertRequest) (*alerts.AcknowledgeAlertResponse, error) {
	req.APIKey = cli.apiKey
	resp, err := cli.sendRequest(cli.buildPostRequest(acknowledgeAlertURL, req))

	if resp == nil {
		return nil, err
	}
	defer resp.Body.Close()

	var acknowledgeAlertResp alerts.AcknowledgeAlertResponse

	if err = resp.Body.FromJsonTo(&acknowledgeAlertResp); err != nil {
		message := "Server response can not be parsed, " + err.Error()
		logging.Logger().Warn(message)
		return nil, errors.New(message)
	}
	return &acknowledgeAlertResp, nil
}