gistfile1.go

package main

import "os"
import "io"
import "encoding/json"

type MyWriters struct {
	StandardOutput io.Writer
	StandardError  io.Writer
	FileOutput     io.Writer
	Everything     io.Writer
}

func main() {

	myFileWriter, err := os.Create("output.json")
	defer myFileWriter.Close()
	if err != nil {
		os.Exit(1)
	}

	out := MyWriters{
		StandardOutput: os.Stdout,
		StandardError:  os.Stderr,
		FileOutput:     myFileWriter,
	}

	out.Everything = io.MultiWriter(os.Stdout, os.Stderr, myFileWriter)

	json.NewEncoder(out.Everything).Encode(struct {
		Name string `json: "name"`
		Age  int    `json: "age"`
	}{
		"Hasse Laugen",
		30,
	})

}