Logger Middleware¶

Logs HTTP requests with method, path, status code, and duration.

Usage¶

Basic Usage¶

app.Use(middleware.Logger)

With Configuration¶

app.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
    Output: os.Stdout,
    Skip: func(c *marten.Ctx) bool {
        return c.Path() == "/health"
    },
}))

Configuration¶

Option	Type	Description
`Output`	`io.Writer`	Where to write logs (default: os.Stdout)
`Format`	`func(...)`	Custom format function
`Skip`	`func(*Ctx) bool`	Skip logging for certain requests
`EnableColors`	`bool`	Enable colored output (default: false)
`JSONFormat`	`bool`	Output logs in JSON format (default: false)

Output¶

GET /users 200 1.234ms 192.168.1.1
POST /users 201 5.678ms 192.168.1.1
GET /users/999 404 0.456ms 192.168.1.1

Examples¶

Basic Logger¶

package main

import (
    "github.com/gomarten/marten"
    "github.com/gomarten/marten/middleware"
)

func main() {
    app := marten.New()

    app.Use(middleware.Logger)

    app.GET("/", func(c *marten.Ctx) error {
        return c.OK(marten.M{"message": "hello"})
    })

    app.Run(":3000")
}

Skip Health Checks¶

app.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
    Skip: func(c *marten.Ctx) bool {
        return c.Path() == "/health" || c.Path() == "/ready"
    },
}))

Custom Output¶

logFile, _ := os.OpenFile("access.log", os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)

app.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
    Output: logFile,
}))

Custom Format¶

app.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
    Format: func(method, path string, status int, duration time.Duration, clientIP string) string {
        return fmt.Sprintf("[%s] %s %s %d %v\n",
            time.Now().Format(time.RFC3339),
            method,
            path,
            status,
            duration,
        )
    },
}))

Colored Output¶

app.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
    EnableColors: true,
}))

Output with ANSI colors: - GET requests in blue - POST requests in green - PUT requests in yellow - DELETE requests in red - 2xx status in green - 4xx status in yellow - 5xx status in red

JSON Format¶

app.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
    JSONFormat: true,
}))

Output:

{"time":"2026-01-14T10:30:00Z","method":"GET","path":"/users","status":200,"duration":"1.234ms","client_ip":"192.168.1.1"}

Custom Logger Middleware¶

For more control, create your own middleware:

func CustomLogger(next marten.Handler) marten.Handler {
    return func(c *marten.Ctx) error {
        start := time.Now()

        err := next(c)

        log.Printf(
            "[%s] %s %s %d %v",
            c.RequestID(),
            c.Method(),
            c.Path(),
            c.StatusCode(),
            time.Since(start),
        )

        return err
    }
}

With Structured Logging¶

func JSONLogger(next marten.Handler) marten.Handler {
    return func(c *marten.Ctx) error {
        start := time.Now()

        err := next(c)

        entry := map[string]any{
            "request_id": c.RequestID(),
            "method":     c.Method(),
            "path":       c.Path(),
            "status":     c.StatusCode(),
            "duration":   time.Since(start).Milliseconds(),
            "client_ip":  c.ClientIP(),
        }

        data, _ := json.Marshal(entry)
        log.Println(string(data))

        return err
    }
}