文件复制

1.使用io包：

func ioCopy(srcName , distName string) (error){
    srcFile ,err := os.Open(srcName)
    if err != nil {
        return   err
    }
    defer srcFile.Close()

    distFile , err := os.Create(distName)
    if err != nil {
        return err
    }
    defer distFile.Close()

    _ , err =  io.Copy(distFile,srcFile)
    return err
}

2.使用os包循环遍历读取写入：

func osReader(srcName , distName string) (error){
    srcFile ,err := os.Open(srcName)
    if err != nil {
        return   err
    }
    defer srcFile.Close()

    distFile , err := os.Create(distName)
    if err != nil {
        return err
    }
    defer distFile.Close()

    buf := make([]byte,1024*4)
    for {
        n ,err := srcFile.Read(buf)
        distFile.Write(buf[:n])
        if err != nil {
            if err == io.EOF {
                break
            }
            return err
        }
    }
    return nil
}

3.使用ioutil包:

func ioutilWriteFile(srcName , distName string) (error){
    copyBytes , err := ioutil.ReadFile(srcName)
    if err != nil {
        return err
    }
    return ioutil.WriteFile(distName,copyBytes,0644)
}