Distinguishing between a missing property and one set to null

[jamesfcarter]

Is there any way of distinguishing between a property that has not been set vs has been set to null, eg

{
  "name": "missing description"
}

vs

{
  "name": "null description",
  "description": null
}

I was hoping to use a null string type to achieve this, but as soon as I set the description property to be nullable: true it converts it into pointer that is nil in both situations. There seems to be a SkipOptionalPointer flag that might do what I need, but I don't see any way of setting that. I'm imagining something like this:

properties:
  name:
    type: string
  description:
    type: string
    nullable: true
    x-skip-optional-pointer: true
    x-go-type: "null.String"
    x-go-type-import:
      path: "gopkg.in/guregu/null.v4"

Is there any way of achieving this?

Thanks.