slogf

slogf sets up a logger based on Go's slog package at 1.21 and enhances features with formatted print.

Installation

go get -u github.com/keithshum/slogf

Use

2 log levels

slogf supports 2 log levels, debug and info. Setting debug to true for debug level while false is info level.
Debug level displays DEBUG, INFO, WARN, ERROR, FATAL logs.
Info level displays INFO, WARN, ERROR, FATAL logs.

2 log formats

slogf supports 2 log formats: text and json.

time=2023-07-11T17:12:46.649Z level=INFO source=main.go:29 msg="Entered main."

{"time":"2023-07-11T17:05:15.924382Z","level":"INFO","source":{"function":"main.main","file":"main.go","line":29},"msg":"Entered main."}

2 log styles

slogf supports 2 log styles.

Extra key value pairs

Debug(), Info(), Warn(), Error(), Fatal() supports extra arguments and attributes.

Way to call: Debug(message, key1, value1, key2, value2) while message is string type value. For passing err directly, just append .Error() afterwards!

Debug("Hello world!", "Hello", "Peter Parker")

{"time":"2023-07-11T17:05:15.924556Z","level":"DEBUG","source":{"function":"main.main","file":"main.go","line":32},"msg":"Hello world!", "Hello":"Peter Parker"}

One-liner print format

Debugf(), Infof(), Warnf(), Errorf(), Fatalf() supports print format style.

Way to call: Debugf(format, substitue)

Debugf("Hello, %v!", "Peter Parker")

{"time":"2023-07-11T17:05:15.924556Z","level":"DEBUG","source":{"function":"main.main","file":"main.go","line":32},"msg":"Hello, Peter Parker!"}

Complete example

package main

import (
    "errors"
    log "github.com/keithshum/slogf"
)

func main() {
    debug := true
    format := "text" // Can be "text" or "json"
    log.InitLogging(debug, format) // One-liner to initiate the logger.

    log.Debug("Dummy debug message", "pod", "MY-POD-1")
    log.Debugf("Dummy debug message. The pod is %v", "MY-POD-1")

    log.Info("Entered main.", "Hello", "Peter Parker!")
    log.Infof("Entered main. %v, %v", "Hello", "Peter Parker!")

    log.Warn("Fake warning.", "pod", "MY-POD-2")
    log.Warnf("Fake warning. The pod is %v", "MY-POD-2")

    err := errors.New("dial tcp: lookup __some_service__: no such host")
    log.Error(err.Error(), "pod", "MY-POD-3")
    log.Errorf("Failed: %v", err.Error())

    log.Fatal("Fatal and exit", "pod", "MY-POD-4")
    log.Fatalf("Fatal and exit, pod = %v", "MY-POD-4") // This line will never get called as program has already exited.
}

[2023-08-29 UTC 23:02:07] /tmp/slogf  $ go run main.go
time=2023-08-29T23:02:19.921Z level=DEBUG source=main.go:13 msg="Dummy debug message" pod=MY-POD-1
time=2023-08-29T23:02:19.921Z level=DEBUG source=main.go:14 msg="Dummy debug message. The pod is MY-POD-1"
time=2023-08-29T23:02:19.921Z level=INFO source=main.go:16 msg="Entered main." Hello="Peter Parker!"
time=2023-08-29T23:02:19.921Z level=INFO source=main.go:17 msg="Entered main. Hello, Peter Parker!"
time=2023-08-29T23:02:19.921Z level=WARN source=main.go:19 msg="Fake warning." pod=MY-POD-2
time=2023-08-29T23:02:19.921Z level=WARN source=main.go:20 msg="Fake warning. The pod is MY-POD-2"
time=2023-08-29T23:02:19.921Z level=ERROR source=main.go:23 msg="dial tcp: lookup __some_service__: no such host" pod=MY-POD-3
time=2023-08-29T23:02:19.921Z level=ERROR source=main.go:24 msg="Failed: dial tcp: lookup __some_service__: no such host"
time=2023-08-29T23:02:19.921Z level=FATAL source=main.go:26 msg="Fatal and exit" pod=MY-POD-4
exit status 1