// Add method creates a heartbeat at OpsGenie.
func (cli *OpsGenieHeartbeatClient) Add(req heartbeat.AddHeartbeatRequest) (*heartbeat.AddHeartbeatResponse, error) {
	req.APIKey = cli.apiKey

	resp, err := cli.sendRequest(cli.buildPostRequest(addHeartbeatURL, req))

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

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

	return &addHeartbeatResp, nil
}