slog

Golang simple logger wrapper. It supports leveled logger with the following levels:

1. PANIC, log message and call panic
2. FATAL, log message and exit by calling os.Exit(1)
3. ERROR, log message in error level
4. WARNING, log message in warning level
5. INFO, log message in info level
6. DEBUG, log message in debug level
7. TRACE, log message in trace level

Logger implements the following interface:

type Logger interface {
    HasLevel(lv Level) bool
    SetLevel(lv Level)

    // Print like methods
    Trace(args ...interface{})
    Debug(args ...interface{})
    Print(args ...interface{})
    Info(args ...interface{})
    Warn(args ...interface{})
    Error(args ...interface{})
    Fatal(args ...interface{})
    Panic(args ...interface{})

    // Println like methods
    Traceln(args ...interface{})
    Debugln(args ...interface{})
    Println(args ...interface{})
    Infoln(args ...interface{})
    Warnln(args ...interface{})
    Errorln(args ...interface{})
    Fatalln(args ...interface{})
    Panicln(args ...interface{})

    // Printf like methods
    Tracef(format string, args ...interface{})
    Debugf(format string, args ...interface{})
    Printf(format string, args ...interface{})
    Infof(format string, args ...interface{})
    Warnf(format string, args ...interface{})
    Errorf(format string, args ...interface{})
    Fatalf(format string, args ...interface{})
    Panicf(format string, args ...interface{})

    // Log with fields (key=value)
    Tracew(msg string, keyVals ...interface{})
    Debugw(msg string, keyVals ...interface{})
    Printw(msg string, keyVals ...interface{})
    Infow(msg string, keyVals ...interface{})
    Warnw(msg string, keyVals ...interface{})
    Errorw(msg string, keyVals ...interface{})
    Fatalw(msg string, keyVals ...interface{})
    Panicw(msg string, keyVals ...interface{})
}

Logger can be initialized with the following constructor

New(name string, w io.Writer, l Level) (Logger, error)
NewWithOptions(w io.Writer, level Level, op Options) (Logger, error)

in which

• name specify logger name. Currently available values discard, stdlog and logrus
• w logger output
• l logger level
• op loger options

Options

1. discard, discard log ouput except panic. Options not supported.

2. stdlog, standar logger options:

   • timestampFormat: timestamp layout format, see time.Time format
   • disableColor: to disable color in log

3. logrus, support options for logrus.TextFormatter formatter and logrus.JSONFormatter formatter.

   • formatter: logrus formatter, either text or json. Default format is logrus.TextFormatter
   • timestampFormat: timestamp layout format, see time.Time format
   • reportCaller: if set to true, the calling method will be added as a field
   • fullTimestamp: logging the full timestamp instead of elapsed time since application started, default to true
   • disableTimestamp: disable timestamp in log
   • fieldMap: customize default key names
   • dataKey: data key for json formatter
   • prettyPrint: pretty print json output
   • disableHTMLEscape: disable HTML escape in json formatter
   • forceColors: for color in text formatter
   • disableColors: disable colors in text formatter
   • forceQuote: force quote in text formatter
   • disableQuote: disable quote in text formatter
   • environmentOverrideColors: override color based on environment config in text formatter
   • disableSorting: disable key sorting in text formatter
   • disableLevelTruncation: disable log level string truncation in text formatter
   • padLevelText: add padding in level string in text formatter
   • quoteEmptyFields: add quote for empty log entry in text formatter

Credits

• Color support via https://github.com/fatih/color
• Logrus logger using https://github.com/sirupsen/logrus

License

The MIT License (MIT), see LICENSE.