Why notfound?

Question

MongoDB

Why does it give "Not found" with such settings. I want answer not to be shown

options := options.FindOne().SetProjection(bson.M{
    "tasks": bson.M{
      "description": 1,
      "answer":      0, // если тут стоит 1 до все ок
      "balls":       1,
    },
  })

The db structure is like this

"tasks": [
    {
        "description":"test description",
        "answer":"test answer",
        "balls":10
    }
]