opensaps/vendor/github.com/pztrn/mogrus/doc/logging_to_mattermost.md

This example presumes:

1. You're using mogrus as logger.

2. You want to log messages from something to Mattermost.

3. You have SendMessage(channelID string, msg string) in your Mattermost's client library for sending messages to desired channel.

4. cl.DebugChannelID is a channel ID to which mogrus will log.

Here's io.Writer-compatible struct for using with mogrus:

var logMessage = `Level: %s
Timestamp: %s
 
    %s`
 
// MattermostChannelLogger provides io.Writer compatible interface for
// writing logs to Mattermost channel.
type MattermostChannelLogger struct{}
 
func (mcl MattermostChannelLogger) Write(p []byte) (n int, err error) {
    // Generate eye-candy message.
    pstr := string(p)
 
    timer := regexp.MustCompile("time=\"([0-9. -:]+)\"")
    timeFound := timer.FindAllStringSubmatch(pstr, -1)
    time := timeFound[0][1]
 
    levelr := regexp.MustCompile("level=([a-zA-Z]+)")
    levelFound := levelr.FindAllStringSubmatch(pstr, -1)
    level := levelFound[0][1]
 
    msgr := regexp.MustCompile("msg=\"(.+)\"")
    msgFound := msgr.FindAllStringSubmatch(pstr, -1)
    logmsg := msgFound[0][1]
 
    msg := fmt.Sprintf(logMessage, level, time, logmsg)
 
    cl.SendMessage(cl.DebugChannelID, msg)
 
    return len(p), nil
}

Initialize it after connecting to Mattermost server like:

// Register output for logging into Mattermost's channel.
c.Log.CreateOutput("Mattermost debug channel", MattermostChannelLogger{}, false, cfg.System.Logging.Level)

Where c.Log is a mogrus instance, cfg.System.Logging.Level is one of logging levels ("debug", "info", "warn" or "error").