Go で非 UTF-8 エンコードされたテキスト ファイル (GBK など) を読み取る方法は?

package main

import (
    "bufio"
    "fmt"
    "log"
    "os"

    "golang.org/x/text/encoding/simplifiedchinese"
    "golang.org/x/text/transform"
)

var enc = simplifiedchinese.GBK

func main() {
    // Example filename
    const filename = "example_GBK_file"

    exampleWriteGBK(filename)
    exampleReadGBK(filename)
}

func exampleReadGBK(filename string) {
    f, err := os.Open(filename)
    if err != nil {
        log.Fatal(err)
    }

    // Convert GBK to UTF-8 on the fly
    r := transform.NewReader(f, enc.NewDecoder())

    sc := bufio.NewScanner(r)
    for sc.Scan() {
        fmt.Printf("Read line: %s\n", sc.Bytes())
    }
    if err := sc.Err(); err != nil {
        log.Fatal(err)
    }
}

func exampleWriteGBK(filename string) {
    f, err := os.Create(filename)
    if err != nil {
        log.Fatal(err)
    }

    w := transform.NewWriter(f, enc.NewEncoder())

    // Example text with Chinese characters
    _, err = fmt.Fprintln(w,
        `In 1995, China National Information Technology Standardization
Technical Committee set down the Chinese Internal Code Specification
(Chinese: 汉字内码扩展规范（GBK）; pinyin: Hànzì Nèimǎ
Kuòzhǎn Guīfàn (GBK)), Version 1.0, known as GBK 1.0, which is a
slight extension of Codepage 936. The newly added 95 characters were not
found in GB 13000.1-1993, and were provisionally assigned Unicode PUA
code points.`)
    if err != nil {
        log.Fatal(err)
    }
}