sigolo

Simple logging helper for go helping you to use log levels, create customizable outputs and to print stack traces.

How to use it

Just call sigolo.{Plain|Info|Debug|Error|Fatal} with a message.

sigolo.Info("Hello world!")
sigolo.Debug("Coordinate: %d, %d", x, y)

The default printing format is something like this:

2018-07-21 01:59:05.431 [INFO]  main.go:21 | Hello world!
2018-07-21 01:59:05.432 [DEBUG] main.go:22 | Coordinate: 42, 13

Only the sigolo.Plain function does not produce leading information (date, log-level, etc.) and just acts like fmt.Printf does.

Error handling

I recommend the pkg/errors package to create and wrap your errors. Why? It enables you to see stack traces ;)

To exit on an error, there's the sigolo.FatalCheck function:

err := someFunctionCall()
sigolo.FatalCheck(err)

When err is not nil, then the error including stack trace will be printed and your application exists with exit code 1.

Log level

Specify the log level by changing sigolo.LogLevel. Possible value are sigolo.LOG_PLAIN, sigolo.LOG_DEBUG , sigolo.LOG_INFO, sigolo.LOG_ERROR and sigolo.LOG_FATAL.

Depending on the log level, some functions will be quite and do not produce outputs anymore:

log level	Methods which will produce an output
`LOG_PLAIN`	`sigolo.Plain()`^* `sigolo.Debug()` `sigolo.Info()` `sigolo.Error()` `sigolo.Fatal()` `sigolo.CheckFatal()` `sigolo.Stack()`
`LOG_DEBUG`	`sigolo.Debug()` `sigolo.Info()` `sigolo.Error()` `sigolo.Fatal()` `sigolo.CheckFatal()` `sigolo.Stack()`
`LOG_INFO`	`sigolo.Info()` `sigolo.Error()` `sigolo.Fatal()` `sigolo.CheckFatal()` `sigolo.Stack()`
`LOG_ERROR`	`sigolo.Error()` `sigolo.Fatal()` `sigolo.CheckFatal()` `sigolo.Stack()`
`LOG_FATAL`	`sigolo.Fatal()` `sigolo.CheckFatal()`
^* Prints to stdout but without any tags in front
^** This will print the error and call `os.Exit(1)`

Function suffixes / Variants

Some functions have a suffix with slightly different behavior.

For non-fatal functions:

Suffix b: Acts like the normal function, but in order to print the correct caller you can go back in the stack.

For fatal-functions:

Suffix f: Acts like the normal function, but after printing the stack, the given format string will be evaluated and printed as well.

Change general output format

The format can be changed by implementing the printing function specified in the sigolo.FormatFunctions array.

Exmaple: To specify your own debug-format:

func main() {
    // Whenever sigolo.Debug is called, our simpleDebug method is used to produce the output.
    sigolo.FormatFunctions[sigolo.LOG_DEBUG] = simpleDebug
    
    sigolo.Debug("Hello world!")
    }
    
    func simpleDebug(writer *os.File, time, level string, maxLength int, caller, message string) {
    // Don't forget the \n at the end ;)
    fmt.Fprintf(writer, "Debug: %s\n", message)
}

This example will print:

Debug: Hello world!

Change time format

To change only the time format, change the value of the sigolo.DateFormat variable. The format of this variable if the format described in the time package.

Example:

func main() {
    // Use the go time formatting string as described in https://pkg.go.dev/time
    sigolo.DateFormat = "02.01.2006 at 15:04:05"
    
    sigolo.Debug("Hello world!")
}

This will produce:

21.07.2018 at 02:16:41 [DEBUG] main.go:37 | Hello world!

hauke96 / sigolo