Sample application to demonstrate the working of "http.Handler" feature in "uber-go/zap".

zap_handler_app.go

// Author: Pravendra Singh (pravj)
// Reference: https://github.com/uber-go/zap/pull/71

// It can be viewed as an application which is trying to load its configurations initially.
// So the log level is `Debug` in starting. The application is emitting both `Info` and `Debug` messages.
// Once the config files are distributed perfectly (simulated by time.Sleep).
// It makes a http request using the provided `Handler` and the log level is changed to `Info`.
// After that the `Debug` messages are ignored.

package main

import (
    "os"
    "fmt"
    "time"
    "net/http"
    "github.com/uber-go/zap"
)

func main() {
    writeSyncer := zap.AddSync(os.Stderr)
    logger := zap.NewJSON(
        zap.Debug,
        zap.Output(writeSyncer),
        zap.ErrorOutput(writeSyncer),
    )

    go func() {
        var i int
        for i <= 4 {
            logger.Debug(fmt.Sprintf("Debug - loading config - time left: %v", 5 - i))
            logger.Info(fmt.Sprintf("Info - loading config - time left: %v", 5 - i))

            time.Sleep(time.Millisecond * 1000)
            i = i + 1
        }

        _, err := http.Get("http://localhost:3000/change")
        if err != nil {
            logger.Fatal("Error in GET request")
        }
        
        // intentionally leaving the check for response data

        i = 1
        for i <= 4 {
            logger.Debug(fmt.Sprintf("Debug - loaded config - since: %v", i))
            logger.Info(fmt.Sprintf("Info - loaded config - since: %v", i))

            time.Sleep(time.Millisecond * 1000)
            i = i + 1
        }

        os.Exit(0)
    }()

    hh := zap.NewHTTPHandler(logger)

    mux := http.NewServeMux()
    mux.Handle("/change", hh.ChangeLogLevel(zap.Info))

    http.ListenAndServe(":3000", mux)
}