My file does not upload to Google Cloud Storage

Hi fellow Gophers,

I am building a small pet app that takes in a file in chunks then uploads it to Google Cloud Blob Storage.
Unfortunately, the file never makes it to Google Cloud (it seems), nothing shows up there. There are no errors.

Does anybody notice anything wrong with this app?
Appreciate any ideas.

func main() {
	router := gin.Default()

	config := cors.DefaultConfig()
	config.AllowAllOrigins = true
	config.AllowHeaders = []string{"Content-Type", "Content-Length", "Content-Range", "Accept-Encoding", "X-CSRF-Token", "Authorization", "accept", "origin", "Cache-Control", "X-Requested-With"}

	rg := router.Group("api/v1")
		rg.POST("/photo", uploadFile)


func uploadFile(c *gin.Context) {
	var f *os.File
	file, header, e := c.Request.FormFile("file")

	if f == nil {
		f, e = os.OpenFile(header.Filename, os.O_APPEND|os.O_CREATE|os.O_RDWR, os.ModeAppend)
		if e != nil {
			panic("Error creating file on the filesystem: " + e.Error())
		defer f.Close()

	if _, e := io.Copy(f, file); e != nil {
		panic("Error during chunk write:" + e.Error())

	if isFileUploadCompleted(c) {
		uploadToGoogle(c, f)

func isFileUploadCompleted(c *gin.Context) bool {
	contentRangeHeader := c.Request.Header.Get("Content-Range")
	rangeAndSize := strings.Split(contentRangeHeader, "/")
	rangeParts := strings.Split(rangeAndSize[0], "-")

	rangeMax, e := strconv.Atoi(rangeParts[1])
	if e != nil {
		panic("Could not parse range max from header")

	fileSize, e := strconv.Atoi(rangeAndSize[1])
	if e != nil {
		panic("Could not parse file size from header")

	return fileSize == rangeMax

func uploadToGoogle(c *gin.Context, f *os.File) {
	creds, isFound := os.LookupEnv("GOOGLE_APPLICATION_CREDENTIALS")
	if !isFound {
		panic("GCP environment variable is not set")
	} else if creds == "" {
		panic("GCP environment variable is empty")
	const bucketName = "el-my-gallery"

	client, e := storage.NewClient(c)
	if e != nil {
		panic("Error creating client: " + e.Error())
	defer client.Close()

	bucket := client.Bucket(bucketName)
	w := bucket.Object(f.Name()).NewWriter(c)
	fmt.Printf("%v is the upload filename", f.Name())

	f.Seek(0, io.SeekStart)
	if bw, e := io.Copy(w, f); e != nil {
		panic("Error during GCP upload:" + e.Error())
	} else {
		fmt.Printf("%v bytes written to Cloud", bw)

For this line fmt.Printf("%v bytes written to Cloud", bw) I do get a lot of bytes written.

The fix was simple, the writer was not closed. :slight_smile:

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