change prefix

download.go

 		return "", "", err
 	}
 	defer r.Body.Close()
-	file, err := ioutil.TempFile(os.TempDir(), "prefix")
+	file, err := ioutil.TempFile(os.TempDir(), "wechat_hitxy_")
 	// Use io.Copy to just dump the response body to the file. This supports huge files
 	_, err = io.Copy(file, r.Body)
 	if err != nil {

upload_test.go

 	SetupConfig()
 	src := "media_for_test/640x480.jpg"
 	mediaID := uploadImage(src)
-	fmt.Printf("get MediaID: %s ", mediaID)
+	fmt.Printf("get MediaID: %s \n", mediaID)
 	//200 OK
 	//{"type":"image","media_id":"3wx8MSvsBYDubAqNi_QZSzNyCrOQ4eoOPslXzpOm6Kzv2Sfh2RngUFlDLfxcSdG2","created_at":1494140549}
 	//mediaID = "3wx8MSvsBYDubAqNi_QZSzNyCrOQ4eoOPslXzpOm6Kzv2Sfh2RngUFlDLfxcSdG2"
 	//mediaID = "L2Cyf6F5GvVXpubv75Pnf51f-Z7Ah5fOROqt1qsZTLmrebtOmeQy9Co2xw7JI6ck"
 	assert.NotEqual(t, mediaID, "", "MediaID should not be Empty")
+
+	//download the media back using the media id
 	filename, e := saveMedia2File(mediaID)
 	log.Println("saved :" + filename)
 	AssertEqual(t, e, nil, "mediaID should be saved without any error")