slog: Fiber middleware

February 14, 2026 · View on GitHub

Fiber middleware to log http requests using slog.

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See also:

slog-multi: slog.Handler chaining, fanout, routing, failover, load balancing...
slog-formatter: slog attribute formatting
slog-sampling: slog sampling policy
slog-mock: slog.Handler for test purposes

HTTP middlewares:

slog-gin: Gin middleware for slog logger
slog-echo: Echo middleware for slog logger
slog-fiber: Fiber middleware for slog logger
slog-chi: Chi middleware for slog logger
slog-http: net/http middleware for slog logger

Loggers:

slog-zap: A slog handler for Zap
slog-zerolog: A slog handler for Zerolog
slog-logrus: A slog handler for Logrus

Log sinks:

slog-datadog: A slog handler for Datadog
slog-betterstack: A slog handler for Betterstack
slog-rollbar: A slog handler for Rollbar
slog-loki: A slog handler for Loki
slog-sentry: A slog handler for Sentry
slog-syslog: A slog handler for Syslog
slog-logstash: A slog handler for Logstash
slog-fluentd: A slog handler for Fluentd
slog-graylog: A slog handler for Graylog
slog-quickwit: A slog handler for Quickwit
slog-slack: A slog handler for Slack
slog-telegram: A slog handler for Telegram
slog-mattermost: A slog handler for Mattermost
slog-microsoft-teams: A slog handler for Microsoft Teams
slog-webhook: A slog handler for Webhook
slog-kafka: A slog handler for Kafka
slog-nats: A slog handler for NATS
slog-parquet: A slog handler for Parquet + Object Storage
slog-channel: A slog handler for Go channels

🚀 Install

# Fiber v3 (current)
go get github.com/samber/slog-fiber

# Fiber v2 (beta)
go get github.com/samber/slog-fiber@fiber-v2

Compatibility: go >= 1.25

No breaking changes will be made to exported APIs before v2.0.0.

💡 Usage

Handler options

type Config struct {
	DefaultLevel     slog.Level
	ClientErrorLevel slog.Level
	ServerErrorLevel slog.Level

	WithUserAgent      bool
	WithRequestID      bool
	WithRequestBody    bool
	WithRequestHeader  bool
	WithResponseBody   bool
	WithResponseHeader bool
	WithSpanID         bool
	WithTraceID        bool
	WithClientIP       bool
	WithCustomMessage  func(c fiber.Ctx, err error) string

	Filters []Filter
}

Attributes will be injected in log payload.

Other global parameters:

slogfiber.TraceIDKey = "trace_id"
slogfiber.SpanIDKey = "span_id"
slogfiber.RequestBodyMaxSize  = 64 * 1024 // 64KB
slogfiber.ResponseBodyMaxSize = 64 * 1024 // 64KB
slogfiber.HiddenRequestHeaders = map[string]struct{}{ ... }
slogfiber.HiddenResponseHeaders = map[string]struct{}{ ... }
slogfiber.RequestIDContextKey = "request-id"
slogfiber.RequestIDHeaderKey = "X-Request-Id"

Minimal

import (
	"github.com/gofiber/fiber/v3"
	"github.com/gofiber/fiber/v3/middleware/recover"
	slogfiber "github.com/samber/slog-fiber"
	"log/slog"
)

// Create a slog logger, which:
//   - Logs to stdout.
logger := slog.New(slog.NewTextHandler(os.Stdout, nil))

app := fiber.New()

app.Use(slogfiber.New(logger))
app.Use(recover.New())

app.Get("/", func(c fiber.Ctx) error {
	return c.SendString("Hello, World 👋!")
})

app.Listen(":4242")

// output:
// time=2023-10-15T20:32:58.926+02:00 level=INFO msg="Incoming request" env=production request.time=2023-10-15T20:32:58.626+02:00 request.method=GET request.path=/ request.route="" request.ip=127.0.0.1:63932 request.length=0 response.time=2023-10-15T20:32:58.926+02:00 response.latency=100ms response.status=200 response.length=7 id=229c7fc8-64f5-4467-bc4a-940700503b0d

OTEL

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

config := slogfiber.Config{
	WithSpanID:  true,
	WithTraceID: true,
}

app := fiber.New()
app.Use(slogfiber.NewWithConfig(logger, config))

Custom log levels

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

config := slogfiber.Config{
	DefaultLevel:     slog.LevelInfo,
	ClientErrorLevel: slog.LevelWarn,
	ServerErrorLevel: slog.LevelError,
}

app := fiber.New()
app.Use(slogfiber.NewWithConfig(logger, config))

Verbose

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

config := slogfiber.Config{
	WithRequestBody: true,
	WithResponseBody: true,
	WithRequestHeader: true,
	WithResponseHeader: true,
}

app := fiber.New()
app.Use(slogfiber.NewWithConfig(logger, config))

Filters

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

app := fiber.New()
app.Use(
	slogfiber.NewWithFilters(
		logger,
		slogfiber.Accept(func (c fiber.Ctx) bool {
			return xxx
		}),
		slogfiber.IgnoreStatus(401, 404),
	),
)
app.Use(recover.New())

Available filters:

Accept / Ignore
AcceptMethod / IgnoreMethod
AcceptStatus / IgnoreStatus
AcceptStatusGreaterThan / IgnoreStatusGreaterThan
AcceptStatusLessThan / IgnoreStatusLessThan
AcceptStatusGreaterThanOrEqual / IgnoreStatusGreaterThanOrEqual
AcceptStatusLessThanOrEqual / IgnoreStatusLessThanOrEqual
AcceptPath / IgnorePath
AcceptPathContains / IgnorePathContains
AcceptPathPrefix / IgnorePathPrefix
AcceptPathSuffix / IgnorePathSuffix
AcceptPathMatch / IgnorePathMatch
AcceptHost / IgnoreHost
AcceptHostContains / IgnoreHostContains
AcceptHostPrefix / IgnoreHostPrefix
AcceptHostSuffix / IgnoreHostSuffix
AcceptHostMatch / IgnoreHostMatch

Using custom time formatters

// Create a slog logger, which:
//   - Logs to stdout.
//   - RFC3339 with UTC time format.
logger := slog.New(
	slogformatter.NewFormatterHandler(
		slogformatter.TimezoneConverter(time.UTC),
		slogformatter.TimeFormatter(time.RFC3339, nil),
	)(
		slog.NewTextHandler(os.Stdout, nil),
	),
)

app := fiber.New()

app.Use(slogfiber.New(logger))
app.Use(recover.New())

app.Get("/", func(c fiber.Ctx) error {
	return c.SendString("Hello, World 👋!")
})

app.Listen(":4242")

// output:
// time=2023-10-15T20:32:58.926+02:00 level=INFO msg="Incoming request" env=production request.time=2023-10-15T20:32:58Z request.method=GET request.path=/ request.route="" request.ip=127.0.0.1:63932 request.length=0 response.time=2023-10-15T20:32:58Z response.latency=100ms response.status=200 response.length=7 id=229c7fc8-64f5-4467-bc4a-940700503b0d

Using custom logger sub-group

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

app := fiber.New()

app.Use(slogfiber.New(logger.WithGroup("http")))
app.Use(recover.New())

app.Get("/", func(c fiber.Ctx) error {
	return c.SendString("Hello, World 👋!")
})

app.Listen(":4242")

// output:
// time=2023-10-15T20:32:58.926+02:00 level=INFO msg="Incoming request" env=production http.request.time=2023-10-15T20:32:58.626+02:00 http.request.method=GET http.request.path=/ http.request.route="" http.request.ip=127.0.0.1:63932 http.request.length=0 http.response.time=2023-10-15T20:32:58.926+02:00 http.response.latency=100ms http.response.status=200 http.response.length=7 http.id=229c7fc8-64f5-4467-bc4a-940700503b0d

Add logger to a single route

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

app := fiber.New()

app.Use(recover.New())

app.Get("/", slogfiber.New(logger), func(c fiber.Ctx) error {
	return c.SendString("Hello, World 👋!")
})

app.Listen(":4242")

Adding custom attributes

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

// Add an attribute to all log entries made through this logger.
logger = logger.With("env", "production")

app := fiber.New()

app.Use(slogfiber.New(logger))
app.Use(recover.New())

app.Get("/", func(c fiber.Ctx) error {
	// Add an attribute to a single log entry.
	slogfiber.AddCustomAttributes(c, slog.String("foo", "bar"))
	return c.SendString("Hello, World 👋!")
})

app.Listen(":4242")

// output:
// time=2023-10-15T20:32:58.926+02:00 level=INFO msg="Incoming request" env=production request.time=2023-10-15T20:32:58.626+02:00 request.method=GET request.path=/ request.route="" request.ip=127.0.0.1:63932 request.length=0 response.time=2023-10-15T20:32:58.926+02:00 response.latency=100ms response.status=200 response.length=7 id=229c7fc8-64f5-4467-bc4a-940700503b0d foo=bar

JSON output

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

app := fiber.New()

app.Use(slogfiber.New(logger))
app.Use(recover.New())

app.Get("/", func(c fiber.Ctx) error {
	return c.SendString("Hello, World 👋!")
})

app.Listen(":4242")

// output:
// {"time":"2023-10-15T20:32:58.926+02:00","level":"INFO","msg":"Incoming request","env":"production","http":{"request":{"time":"2023-10-15T20:32:58.626+02:00","method":"GET","path":"/","route":"","ip":"127.0.0.1:55296","length":0},"response":{"time":"2023-10-15T20:32:58.926+02:00","latency":100000,"status":200,"length":7},"id":"04201917-d7ba-4b20-a3bb-2fffba5f2bd9"}}

🤝 Contributing

Ping me on twitter @samuelberthe (DMs, mentions, whatever :))
Fork the project
Fix open issues or request new features

Don't hesitate ;)

# Install some dev dependencies
make tools

# Run tests
make test
# or
make watch-test

👤 Contributors

Contributors

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📝 License

This project is MIT licensed.