如何在 Go 中高效地从文件中读取一行作为字符串？

import (
    "bufio"
    "fmt"
    "os"
)

func readln(r *bufio.Reader) (string, error) {
    var (
        isPrefix bool = true
        err error = nil
        line, ln []byte
    )
    for isPrefix && err == nil {
        line, isPrefix, err = r.ReadLine()
        ln = append(ln, line...)
    }
    return string(ln), err
}

func main() {
    f, err := os.Open(fi)
    if err != nil {
        fmt.Println("error opening file= ", err)
        os.Exit(1)
    }
    r := bufio.NewReader(f)
    s, e := readln(r)
    for e == nil {
        fmt.Println(s)
        s, e = readln(r)
    }
}