The tar.Reader docs give this example:

tr := tar.NewReader(r)
for {
    hdr, err := tr.Next()
    if err != nil {
        // handle error
    }
    if hdr == nil {
        // end of tar archive
        break
    }
    io.Copy(data, tr)
}

But when I tried it it failed because I hit EOF. So either the tar package isn't working
correctly (i.e., not as documented), or the example needs to be changed to something
like this (which I've tried and works):

tr := tar.NewReader(r)
for {
    hdr, err := tr.Next()
    if err != nil {
                if err == os.EOF {
                    break
                }
        // handle error
    }
    if hdr == nil {
        // end of tar archive
        break
    }
    io.Copy(data, tr)
}