使用Golang从Google的数据存储区获取ID

I have a Go struct:

type Foo struct{
  Name: string
  Age: int
}

I am able to save and retrieve Foos in datastore. So I may edit a Foo, I want to get the ID that datastore assigns a Foo, to use in an anchor. I verified that IDs are assigned using Google's datastore dashboard, but how do I get the ID off of a retrieved Foo?

GetAll returns the keys along with any error.

keys, err := q.GetAll(c, &foos)

keys is an array of datastore.Key