package hello
import (
    "fmt"
    "net/http"
    "google.golang.org/appengine"
    "google.golang.org/appengine/image"
    "google.golang.org/appengine/blobstore"
)
func init() {
    http.HandleFunc("/", handler)
}
func handler(w http.ResponseWriter, r *http.Request) {
    c := appengine.NewContext(r)
    blobKey,err := blobstore.BlobKeyForFile(c, "/gs/foo-999.appspot.com/photos/bar.jpg")
    url, urlErr := image.ServingUrl(c, blobKey)
    fmt.Fprint(w, url)
}