Go - Fail to download from s3 using s3manager - amazon-web-services

Question

I'm using the script from this post to download files from s3.
Everything works fine except the downloaded files are all 0B.
My script are basically the same as the script above.
I use ~/.aws/credentials to set my keys and set region in the script.
Here is my script:
package main
import (
"fmt"
"os"
"path/filepath"
"github.com/aws/aws-sdk-go/service/s3"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/service/s3/s3manager"
)
var (
Bucket = "logs" // Download from this bucket
Prefix = "local-dir/my_log/20150611/20150611" // Using this key prefix
LocalDirectory = "s3logs" // Into this directory
)
func main() {
manager := s3manager.NewDownloader(nil)
d := downloader{bucket: Bucket, dir: LocalDirectory, Downloader: manager}
client := s3.New(&aws.Config{Region: "ap-northeast-1"})
params := &s3.ListObjectsInput{Bucket: &Bucket, Prefix: &Prefix}
client.ListObjectsPages(params, d.eachPage)
}
type downloader struct {
*s3manager.Downloader
bucket, dir string
}
func (d *downloader) eachPage(page *s3.ListObjectsOutput, more bool) bool {
for _, obj := range page.Contents {
d.downloadToFile(*obj.Key)
}
return true
}
func (d *downloader) downloadToFile(key string) {
// Create the directories in the path
file := filepath.Join(d.dir, key)
if err := os.MkdirAll(filepath.Dir(file), 0775); err != nil {
panic(err)
}
fmt.Printf("Downloading " + key)
// Setup the local file
fd, err := os.Create(file)
if err != nil {
panic(err)
}
defer fd.Close()
// Download the file using the AWS SDK
fmt.Printf("Downloading s3://%s/%s to %s...\n", d.bucket, key, file)
params := &s3.GetObjectInput{Bucket: &d.bucket, Key: &key}
d.Download(fd, params)
}
The script listed the objects in the bucket very well, but did not download files into my local file system. And the script did not run into any exception.
Any idea why?
Thanks!