将文件复制到文件夹中，直到达到一定大小

I have a folder named "myfolder" that has some txt and jpeg files and and a folder named "test". I want to copy files inside myfolder to test until it reaches a certain size, for example 10MB, then stop to copy.

This is my code that does not work:

package main

import (
    "errors"
    "fmt"
    "io/ioutil"
    "os"
    "path/filepath"
    "strconv"
)

var (
    MyFolderPath = "/home/jim/myfolder"
    files        []string
)

func copy(source []string, destination string) {

    for a, b := range source {
        input, _ := ioutil.ReadFile(b)
        ioutil.WriteFile(destination+strconv.Itoa(a), input, 0777)
    }

}

func CopyFile(path string) {
    var size int64
    done := errors.New("size reached")
    err := filepath.Walk(path, func(_ string, info os.FileInfo, err error) error {
        if err != nil {
            return err
        }
        copy(files[1:], fmt.Sprintf("%v/test/%v", MyFolderPath, "file"))
        size += info.Size()

        if size > 10000 {
            return done
        }

        return err

    })
    if err != nil {
        fmt.Println(err)
    }

}

func CollectFiles() {
    err := filepath.Walk(MyFolderPath, func(path string, info os.FileInfo, err error) error {
        if err != nil {
            fmt.Println(err)
        }
        files = append(files, path)
        return nil

    })
    if err != nil {
        fmt.Println(err)
    }
}

func main() {
    CollectFiles()
    CopyFile(fmt.Sprintf("%v/test", MyFolderPath))
}

What I do wrong and how can I do in right way?

You have multiple places where you're wrong. Perhaps check this code and compare:

package main

import (
    "errors"
    "fmt"
    "os"
    "path/filepath"
)

var (
    MyFolderPath   = "/tmp"
    DestPath       = "/tmp/dest"
    CumulativeSize int64 = 0 // in bytes
    ErrDone = errors.New("done")
)

const UpperLimit = 1024 * // 1 Kilobyte
    1024 * // 1 Megabyte
    10 // 10 Megabytes

func main() {
    err := filepath.Walk(MyFolderPath, func(path string, info os.FileInfo, err error) error {
        if err != nil {
            fmt.Printf("problem with file (%s): %v", path, err)
            return nil
        }
        if info.IsDir() {
            return filepath.SkipDir // skip it, walk will enter it too
        }
        CumulativeSize += info.Size()

        if CumulativeSize >= UpperLimit {
            return ErrDone
        }

        // copy file here

        return nil
    })

    if err == ErrDone {
        fmt.Println("finished successfully")
    } else {
        fmt.Printf("error: %v", err)
    }
}

This line is wrong:

    copy(files[1:], fmt.Sprintf("%v/test/%v", MyFolderPath, "file"))

Every time you find a file match, you tell it to (re)-copy every file in your files slice, except the first one.

You probably want to copy a single file there.

Although your code is difficult to reason through--I'm not sure why files exists at all, nor why you're walking your directory structure twice. So your goals aren't really clear, so it's hard to be more specific.

Also note: You should not use copy as the name of a function, as that is a built-in, so makes your code very confusing to read.