Structured Request Logs with slog

Zinc’s request logger uses log/slog directly. Supply the logger your service already uses and choose the request fields that belong in production logs.

Setup

mkdir zinc-logging
cd zinc-logging
go mod init example.com/zinc-logging
go get github.com/0mjs/zinc

Application

package main

import (
  "log"
  "log/slog"
  "os"

  "github.com/0mjs/zinc"
  "github.com/0mjs/zinc/middleware"
)

func main() {
  logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
    Level: slog.LevelInfo,
  }))

  loggerConfig := middleware.DefaultRequestLoggerConfig()
  loggerConfig.Logger = logger
  loggerConfig.LogRoutePath = true
  loggerConfig.LogHeaders = []string{"Traceparent"}

  app := zinc.New()
  app.Use(
    middleware.RequestID(),
    middleware.RequestLoggerWithConfig(loggerConfig),
    middleware.Recover(),
  )

  app.Get("/users/{id}", func(c *zinc.Context) error {
    return c.JSON(zinc.Map{
      "id":         c.Param("id"),
      "request_id": c.RequestID(),
    })
  })

  log.Fatal(app.Listen(":8080"))
}

Try it

curl http://localhost:8080/users/42

The log record includes latency, method, URI, status, remote IP, request ID, content length, response size, and the selected Traceparent header. Avoid logging authorization, cookie, or other secret-bearing headers.

For complete control, set RequestLoggerConfig.LogValuesFunc. It receives a RequestLoggerValues snapshot and can map fields into an existing logging or observability pipeline.