Return io.ReadCloser from zip.NewWriter - go

Question

I am creating a buffer and then writing into that buffer via zip.NewWriter()
So my code looks like this
// Create a buffer to write our archive to.
buf := new(bytes.Buffer)
// Create a new zip archive.
w := zip.NewWriter(buf)
// Create file in this writer
f, err := w.Create("test.json")
/ Writing data to file
_, _ = f.Write([]byte("some data"))
// Close writer
_ = w.Close()
// TODO: Return this data in the form of io.ReadCloser
My end goal is to write files into this zip writer and return the data in the form of io.ReadCloser, my calling function expects data in io.ReadCloser
I tried to find and try multiple ways but none of them succeeded.

Answer 1

Check if this example works for you
func ExampleWriter() {
// Create a buffer to write our archive to.
buf := new(bytes.Buffer)
// Create a new zip archive.
w := zip.NewWriter(buf)
// Add some files to the archive.
var files = []struct {
Name, Body string
}{
{"readme.txt", "This archive contains some text files."},
{"gopher.txt", "Gopher names:\nGeorge\nGeoffrey\nGonzo"},
{"todo.txt", "Get animal handling licence.\nWrite more examples."},
}
for _, file := range files {
f, err := w.Create(file.Name)
if err != nil {
log.Fatal(err)
}
_, err = f.Write([]byte(file.Body))
if err != nil {
log.Fatal(err)
}
}
// Make sure to check the error on Close.
err := w.Close()
if err != nil {
log.Fatal(err)
}
}
By systematically check the error for those operations, you will see if there are any issue.

Answer 2

After some help from comments I got it working
So we can directly convert buf to io.ReadCloser and return it, no need for further conversion.
func ExampleWriter() (io.ReadCloser, error) {
// Create a buffer to write our archive to.
buf := new(bytes.Buffer)
// Create a new zip archive.
w := zip.NewWriter(buf)
// Add some files to the archive.
var files = []struct {
Name, Body string
}{
{"readme.txt", "This archive contains some text files."},
{"gopher.txt", "Gopher names:\nGeorge\nGeoffrey\nGonzo"},
{"todo.txt", "Get animal handling licence.\nWrite more examples."},
}
for _, file := range files {
f, err := w.Create(file.Name)
if err != nil {
log.Fatal(err)
}
_, err = f.Write([]byte(file.Body))
if err != nil {
log.Fatal(err)
}
}
// Make sure to check the error on Close.
err := w.Close()
if err != nil {
log.Fatal(err)
}
return ioutil.NopCloser(buf), nil // This returns io.ReadCloser
}