Go言語で文字コード変換 ref: http://qiita.com/uchiko/items/1810ddacd23fd4d3c934

encode.go

package main

import (
        "code.google.com/p/go.text/encoding/japanese"
        "code.google.com/p/go.text/transform"
        "fmt"
        "io/ioutil"
        "strings"
)

// UTF-8 から ShiftJIS
func utf8_to_sjis(str string) (string, error) {
        ret, err := ioutil.ReadAll(transform.NewReader(strings.NewReader(str), japanese.ShiftJIS.NewEncoder()))
        if err != nil {
                return "", err
        }
        return string(ret), err
}


// ShiftJIS から UTF-8
func sjis_to_utf8(str string) (string, error) {
        ret, err := ioutil.ReadAll(transform.NewReader(strings.NewReader(str), japanese.ShiftJIS.NewDecoder()))
        if err != nil {
                return "", err
        }
        return string(ret), err
}

// UTF-8 から EUC-JP
func utf8_to_eucjp(str string) (string, error) {
        ret, err := ioutil.ReadAll(transform.NewReader(strings.NewReader(str), japanese.EUCJP.NewEncoder()))
        if err != nil {
                return "", err
        }
        return string(ret), err
}

// EUC-JP から UTF-8
func eucjp_to_utf8(str string) (string, error) {
        ret, err := ioutil.ReadAll(transform.NewReader(strings.NewReader(str), japanese.EUCJP.NewDecoder()))
        if err != nil {
                return "", err
        }
        return string(ret), err
}

func main() {
        str := "テスト"
        msg, err := utf8_to_sjis(str)
        if err != nil {
                panic(err)
        }
        msg, err = sjis_to_utf8(msg)
        fmt.Println(msg)
}

shell

go get code.google.com/p/go.text/encoding
go get code.google.com/p/go.text/encoding/japanese