How to initialize a zap logger once and reuse it in other Go files?


I’m trying to migrate my application from the beautiful Logrus (very helpful for debug) and introducing the Uber log framework Zap.

With Logrus, I can initialize the logger only once and reuse it from other Go file, an example:

package main
    // Print filename on log
    filename ""
    // Very nice log library
    log ""

func main(){

    Formatter := new(log.TextFormatter)
    Formatter.TimestampFormat = "Jan _2 15:04:05.000000000"
    Formatter.FullTimestamp = true
    Formatter.ForceColors = true
    log.AddHook(filename.NewHook()) // Print filename + line at every log


From other Go file, I’m able to reuse that logger without any other initialization:

// VerifyCommandLineInput is delegated to manage the inputer parameter provide with the input flag from command line
func VerifyCommandLineInput() datastructures.Configuration {
    log.Debug("VerifyCommandLineInput | Init a new configuration from the conf file")
    c := flag.String("config", "./conf/test.json", "Specify the configuration file.")
    if strings.Compare(*c, "") == 0 {
        log.Fatal("VerifyCommandLineInput | Call the tool using --config conf/config.json")
    file, err := os.Open(*c)
    if err != nil {
        log.Fatal("VerifyCommandLineInput | can't open config file: ", err)
    defer file.Close()
    decoder := json.NewDecoder(file)
    cfg := datastructures.Configuration{}
    err = decoder.Decode(&cfg)
    if err != nil {
        log.Fatal("VerifyCommandLineInput | can't decode config JSON: ", err)
    log.Debug("VerifyCommandLineInput | Conf loaded -> ", cfg)

    return cfg

My question is: using the Zap log framework, how can I initialize the log in the main function and use that logger from the other Go file?


You can set up your logger in the main function and call zap.ReplaceGlobals to use it as a default global logger.

ReplaceGlobals replaces the global Logger and SugaredLogger, and returns a function to restore the original values. It’s safe for concurrent use.

Answered By – Mikhail

Answer Checked By – David Goodson (GoLangFix Volunteer)

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