Golang MongoDB查询

Question

How to i query mongodb using golang bson to retrieve the ipv4Address field in the document. Am using the nfType field as a query parameter.

currently, mongo distinct out only array of the form

var ip []string
    query := bson.M{"nfType": "SMF"}
    err := db.C(COLLECTION).Find(query).Distinct("ipv4Addresses", &ip)

result

["198.51.100.1"] 

however, I​ want the field as

{ "ipv4Addresses": [ "198.51.100.1"] } 

or

[{ "ipv4Addresses": [ "198.51.100.1"] }]

The JSON document in the collection is of the form

{
  "nfType": [
    "SMF"
  ],
  "nfStatus": [
    "REG"
  ],
  "sNssais": [
    {
      "sst": 1,
      "sd": "sd1"
    }
  ],
  "nsiList": [
    "NSI-ID1"
  ],
  "ipv4Addresses": [
    "198.51.100.1"
  ]
}