🧻 devslog - Go slog.Handler for development

devslog is a zero dependency structured logging handler for Go's log/slog package with pretty and colorful output for developers.

Devslog output

Compared to

TextHandler

JSONHandler

Install

go get github.com/golang-cz/devslog@latest

Examples

Logger without options

logger := slog.New(devslog.NewHandler(os.Stdout, nil))

// optional: set global logger
slog.SetDefault(logger)

Logger with custom options

// new logger with options
opts := &devslog.Options{
	MaxSlicePrintSize: 4,
	SortKeys:          true,
	TimeFormat:        "[04:05]",
	NewLineAfterLog:   true,
	DebugColor:        devslog.Magenta,
}

logger := slog.New(devslog.NewHandler(os.Stdout, opts))

// optional: set global logger
slog.SetDefault(logger)

Logger with default slog options

Handler accepts default slog.HandlerOptions

// slog.HandlerOptions
slogOpts := &slog.HandlerOptions{
	AddSource:   true,
	Level:       slog.LevelDebug,
}

// new logger with options
opts := &devslog.Options{
	HandlerOptions:    slogOpts,
	MaxSlicePrintSize: 4,
	SortKeys:          true,
	NewLineAfterLog:   true,
}

logger := slog.New(devslog.NewHandler(os.Stdout, opts))

// optional: set global logger
slog.SetDefault(logger)

Example usage

slogOpts := &slog.HandlerOptions{
	AddSource: true,
	Level:     slog.LevelDebug,
}

var logger *slog.Logger
if production {
	logger = slog.New(slog.NewJSONHandler(os.Stdout, slogOpts))
} else {
	opts := &devslog.Options{
		HandlerOptions:    slogOpts,
		MaxSlicePrintSize: 10,
		SortKeys:          true,
		NewLineAfterLog:   true,
	}

	logger = slog.New(devslog.NewHandler(os.Stdout, opts))
}

// optional: set global logger
slog.SetDefault(logger)

Options

Parameter	Description	Default	Value
MaxSlicePrintSize	Specifies the maximum number of elements to print for a slice.	50	uint
SortKeys	Determines if attributes should be sorted by keys.	false	bool
TimeFormat	Time format for timestamp.	"[15:04:05]"	string
NewLineAfterLog	Add blank line after each log	false	bool
DebugColor	Color for Debug level	devslog.Blue	devslog.Color (uint)
InfoColor	Color for Info level	devslog.Green	devslog.Color (uint)
WarnColor	Color for Warn level	devslog.Yellow	devslog.Color (uint)
ErrorColor	Color for Error level	devslog.Red	devslog.Color (uint)
MaxErrorStackTrace	Max stack trace frames for errors	0	uint