I'm having trouble setting the cache-control max-age header for images in my storage bucket. The images are actually stored in a firebase storage bucket, if that makes any difference.

I can successfully upload an image receive the file object in the response. I then set the cache-control max-age header for the file to 31536000 like:

```
const gcloud = require('google-cloud');
const gcs = gcloud.storage({credentials: myCredentials});
const storageBucket = gcs.bucket(myConfig);

storageBucket.upload('path/to/image', {
    public: true,
    destination: storageBucket.file('storageBucketName/imageName.png')
} , (err, file, apiResponse) => {
    file.setMetadata({
        cacheControl: 'public, max-age=31536000'
     });
});

```

When I visit the image at the public url (<https://storage.googleapis.com/my-bucket-name.appspot.com/storageBucketName/imageName.png>) the cache-control max-age header is set to 3600, which is the default.

Oddly enough if I visit the public url over **http** (<http://storage.googleapis.com/my-bucket-name.appspot.com/storageBucketName/imageName.png>) the cache-control max-age header is set to 31536000, as expected.

How can I set this header for the public url available over https? Thanks!