golang io 读取文件

package main

import (
    "fmt"
    "io/ioutil"
    "log"
    "strings"
)

func main() {
    r := strings.NewReader("Go is a general-purpose language designed with systems programming in mind.")
    b, err := ioutil.ReadAll(r)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("%s", b)

    dir, err := ioutil.ReadDir("../")
    if err != nil {
        log.Fatal(err)
    }
    for _, file := range dir {
        fmt.Println(file.Name())
    }

    b, err = ioutil.ReadFile("./main.go")
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("%s", b)
}