Go pretty print JSON

pj.go

package main

import (
	"bytes"
	"encoding/json"
	"io"
	"io/ioutil"
	"os"
)

func main() {
	var stream io.Reader
	if len(os.Args) > 1 {
		file, err := os.Open(os.Args[1])
		if err != nil {
			os.Stderr.Write([]byte(err.Error()))
			os.Exit(1)
		}
		defer file.Close()
		stream = file
	} else {
		stream = os.Stdin
	}
	var out bytes.Buffer
	buffer, err := ioutil.ReadAll(stream)
	if err != nil {
		os.Stderr.Write([]byte(err.Error()))
		os.Exit(1)
	}
	json.Indent(&out, buffer, "", "\t")
	out.WriteTo(os.Stdout)
}