有关peek在实际应用中的疑问

请问在这一串代码中resp.body为什么会从第1025个字符开始读取 但是bodyReader就没事呢,感觉resp.body也没被处理呀

package fetcher

import (
    "bufio"
    "fmt"
    "golang.org/x/net/html/charset"
    "golang.org/x/text/encoding"
    "golang.org/x/text/encoding/unicode"
    "golang.org/x/text/transform"
    "io/ioutil"
    "log"
    "net/http"
)

const url = "http://www.zhenai.com/zhenghun"

func Fetch(url string) ([]byte, error) {
    resp, err := http.Get(url)
    if err != nil {
        return nil, err
    }
    defer resp.Body.Close()

    if resp.StatusCode != http.StatusOK {
        return nil,
            fmt.Errorf("wrong status code: %d", resp.StatusCode)
    }

    bodyReader := bufio.NewReader(resp.Body)
    e := determinEncoding(bodyReader)
    utf8Reader := transform.NewReader(resp.Body, e.NewDecoder())  // !!!!!问题出在这里
    return ioutil.ReadAll(utf8Reader)

}

func determinEncoding(
    r *bufio.Reader) encoding.Encoding {
    bytes, err := r.Peek(1024)
    if err != nil {
        log.Printf("Fetcher error: %v", err)
        return unicode.UTF8
    }
    e, _, _ := charset.DetermineEncoding(bytes, "")
    return e
}