创建存储桶文件时出现MediaLink问题

I am using GoLang along as Google App Engine for hosting my web services.

I have been succesful in creating a file to my Firebase storage bucket, but then I would like to get a clean url for it that can be retrieved by clients (iOS / Android) that are authentified with firebase Auth.

What would be the easiest way to get such a link ?

What I have tried :

Getting ObjAttrs object, the bucket object attributes after the creation of the file : This way in Go

attrs, err := obj.Attrs(ctx)

and I do get the attributes, among them a value called MediaLink

A sample of this link would be "https://www.googleapis.com/download/storage/v1/b/MY_BUCKET/o/MY_FOLDER%2FMY_FILE_NAME?generation=1539262480095558&alt=media"

Problems :

If I try to open this link into a browser, I get the following error : "Anonymous caller does not have storage.objects.get access to...."

Fair enough, since I'm not authentified with Firebase Auth at this point

But I also tried from a iOS client which is properly authentified with Firebase Auth, and still the retrieval of the link failed.

On the web console, attached to my file in my bucket, I see a link such as this "https://firebasestorage.googleapis.com/v0/b/MY_BUCKET/o/MY_FOLDER%2FMY_FILENAME?alt=media&token=47630584-f05c-43a2-a04d-8fc21d207181"

This works on both browser and iOS clients.

Now is how can I get by code, in GOLang such URL ?

I have seen no documentation about this.