有没有办法通过Elasticsearch查询故意返回null值？

I have to return an elasticsearch query in my code (Golang using olivere's elastic v.5 library) and if a particular condition occurs, I want to be able to pass in a query that will take minimal time and always return null. Is there a standard way to do this? I tried using a Term query with empty strings as parameters:

elastic.NewTermQuery("", "")

But this doesn't seem to be a valid query. Is there a good way to do this?

If by "always return null" you mean match nothing:

{
    "bool": {
        "must_not": {
            "match_all": {}
        }
    }
}

I'm sure match_all is implemented very efficiently.