Construct MongoDB query from GraphQL request

Let’s say we query the server with this request, we only want to get the following user’s Email, My current implementation requests the whole User object from the MongoDB, which I can imagine is extremely inefficient.

GQL
{
  user(id:"34567345637456") {
    email
  }
}

How would you go about creating a MongoDB filter that would only return those Specified Fields? E.g,

JS object
{
   "email": 1
}

My current server is running Node.js, Fastify and Mercurius