main.go

package main

import (
	"time"

	"github.com/rs/zerolog"
	"gopkg.in/natefinch/lumberjack.v2"
)

func main() {
	zerolog.TimeFieldFormat = time.RFC3339Nano

	writer := &lumberjack.Logger{
		Filename: "test.log",
		// メガバイト
		MaxSize:    10,
		MaxBackups: 5,
		// 日
		MaxAge: 1,
		// デフォルトは無効
		Compress: true,
	}

	log := zerolog.New(writer).With().Logger()

	log.Log().
		Timestamp().
		Int("baz", 123).
		Msg("hello world")
}

test.log にこんな感じで記録されていきます。

{"time":"2020-01-02T00:38:35.060001+09:00","baz":123,"message":"hello world"}
{"time":"2020-01-02T00:38:49.866742+09:00","baz":123,"message":"hello world"}
{"time":"2020-01-02T00:40:17.398441+09:00","baz":123,"message":"hello world"}
{"time":"2020-01-02T00:40:52.711166+09:00","baz":123,"message":"hello world"}
{"time":"2020-01-02T00:40:55.236672+09:00","baz":123,"message":"hello world"}
{"time":"2020-01-02T00:40:57.601786+09:00","baz":123,"message":"hello world"}
{"time":"2020-01-02T00:46:20.994704+09:00","baz":123,"message":"hello world"}