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github.com/thecodinglab/log is another structured logging library for Golang. It has been inspired by some other awesome logging libraries such as logrus and zap.

I started with this library to combine my personal logging stack into a single library which I can simply import in all of my projects. I am still heavily working on this, so I don't recommend using it in production. However, if you have any feedback or suggestions, feel free to open an issue or pull request.

Usage

go get -u github.com/thecodinglab/log

The logging API uses the golang context package to pass instances of the log.Logger interface through the application. By doing this, each module can append additional meta information to the logger without having to pass a logging instance to every sub-service it uses.

• Application → initialize logging
  • RESTful API Service → attach HTTP client information
    • Database → attach query statement
    • ...
  • ...

package main

import (
	"context"
	"net"
	"net/http"
	"os"

	"github.com/thecodinglab/log"
	"github.com/thecodinglab/log/level"
	"github.com/thecodinglab/log/capture"
	"github.com/thecodinglab/log/sinks/file"
)

func main() {
	// initialize logger to print to stdout
	logger := log.New(
		file.New(os.Stdout, file.TextFormatter{}, level.Info),
	)
	defer logger.Sync()

	// attach the logger to the global application context
	ctx := log.Attach(context.Background(), logger)

	router := http.NewServeMux()

	server := &http.Server{
		Addr:    "0.0.0.0:8080",
		Handler: loggingMiddleware(router),

		// use the previously created application context as base context for each request
		BaseContext: func(listener net.Listener) context.Context {
			return ctx
		},
	}

	if err := server.ListenAndServe(); err != nil {
		capture.Error(ctx, err)
	}
}

func loggingMiddleware(base http.Handler) http.Handler {
	return http.HandlerFunc(func(res http.ResponseWriter, req *http.Request) {
		// attach client information to the logger
		logger := log.With(req.Context(),
			"client", req.RemoteAddr,
			"request_method", req.Method,
			"request_url", req.URL.String(),
		)

		logger.Debug("client ", req.RemoteAddr, " requested resource ", req.URL)

		// pass client information down to the next handler
		ctx := log.Attach(req.Context(), logger)
		base.ServeHTTP(res, req.WithContext(ctx))
	})
}