package main

import (
    "fmt"
    "io/ioutil"
    "os"
)

func main() {
    filename := "a.txt"
    //--------- create file ----------
    file, err := os.Create(filename)
    if err != nil {
        fmt.Println(err)
    }
    defer file.Close()

    str := "你好,世界"
    data := []byte(str)

    err = ioutil.WriteFile(filename, data, 066)

    //--------- read file ------------
    buf := make([]byte, 20)
    n, err := file.Read(buf)
    if err != nil {
        fmt.Println(err)
    }
    fmt.Printf("------------method 1-------------\n%v\n", buf)
    fmt.Printf("--> 读取长度:%v\n", n)
    fmt.Printf("--> %v,\n", string(buf))

    //------------ read file method 2 ---------
    res, err := ioutil.ReadFile(filename)
    if err != nil {
        fmt.Println(err)
    }
    fmt.Println("---------- method 2----------")
    fmt.Println(string(res))

}

$ go run main.go 
------------method 1-------------
[228 189 160 229 165 189 44 228 184 150 231 149 140 0 0 0 0 0 0 0]
--> 读取长度:13
--> 你好,世界,
---------- method 2----------
你好,世界