Part of https://jacoposalvestrini.medium.com/batch-download-files-from-aws-s3-36e575f30682

AWSS3-BatchDownload-buffer.go

type buffer struct {
	Path string

	buf *aws.WriteAtBuffer
}

func (b *buffer) WriteAt(p []byte, off int64) (n int, err error) {
	if b.buf == nil {
		b.buf = &aws.WriteAtBuffer{}
	}
	return b.buf.WriteAt(p, off)
}

func (b *buffer) Save() (n int, err error) {
	if b.buf == nil {
		return
	}
	var f *os.File
	f, err = os.Create(b.Path)
	if err != nil {
		return
	}
	defer f.Close()
	n, err = f.Write(b.buf.Bytes())
	return
}