rot13 implementation

main.go

package main

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

type rot13Reader struct {
    r io.Reader
}

func (reader rot13Reader) Read(p []byte) (int, error) {
    n, err := reader.r.Read(p)
    if err != nil {
        return n, err
    }

    for index := 0; index <= n-1; index++ {
        value := p[index]
        if value < 65 || value > 122 {
            continue
        }

        if (value > 77 && value < 90) || value > 109 {
            p[index] -= 13
        } else {
            p[index] += 13
        }
    }

    return n, err
}

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