[storage emulator] Written 3 bytes but got 5 bytes #3556

package main

import (
	"context"
	"io/ioutil"
	"log"
	"net/http"
	"net/url"

	"cloud.google.com/go/storage"
	"google.golang.org/api/option"
)

type roundTripper url.URL

func (rt roundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
	req.Host = rt.Host
	req.URL.Host = rt.Host
	req.URL.Scheme = rt.Scheme
	return http.DefaultTransport.RoundTrip(req)
}

func main() {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	u, _ := url.Parse("http://localhost:9199")
	hClient := &http.Client{Transport: roundTripper(*u)}
	cs, err := storage.NewClient(context.Background(), option.WithHTTPClient(hClient))

	if err != nil {
		log.Fatalln("Failed firebase app to storage.", err)
	}

	b := cs.Bucket("default-bucket")

	{
		w := b.Object("f1").NewWriter(ctx)
		dat := "123"
		n, _ := w.Write([]byte(dat))
		log.Printf("Bytes written %q (size %d)\n", dat, n)
		if err := w.Close(); err != nil {
			log.Fatalln("Failed write file.", err)
		}
	}

	{
		r, err := b.Object("f1").NewReader(ctx)
		if err != nil {
			log.Fatalln("Failed open file.", err)
		}
		dat, err := ioutil.ReadAll(r)
		if err != nil {
			log.Fatalln("Failed read file.", err)
		}
		if err := r.Close(); err != nil {
			log.Fatalln("Failed write file.", err)
		}
		log.Printf("Got data %q (size %d)\n", string(dat), r.Size())
	}

}