GO Exercise: rot13Reader - http://tour.golang.org/methods/12

rot13Reader.go

package main

import (
	"io"
	"os"
	"strings"
)

type rot13Reader struct {
	r io.Reader
}

func (this *rot13Reader) Read(bytes []byte) (num int, err error) {
	num, err = this.r.Read(bytes)
	for index := range bytes {
		if (bytes[index] >= 'A' && bytes[index] <= 'M') || (bytes[index] >='a' && bytes[index] <= 'm') {
			bytes[index] += 13
		} else if (bytes[index] >= 'N' && bytes[index] <= 'Z') || (bytes[index] >= 'n' && bytes[index] <= 'z'){
			bytes[index] -= 13
		}
	}
	return
}

func main() {
	s := strings.NewReader("Lbh penpxrq gur pbqr!")
	r := rot13Reader{s}
	io.Copy(os.Stdout, &r)
}