How to write go bson.M from MongoDb query

I am using mongodb as database. I'm able to query the database from the command line using the command

db.nfinstances.distinct("ipv4Addresses",{"nfType":"AMF", "amfInfo.amfSetId": "3fa85f64-5717-4562-b3fc-2c963f66af33"})

and this give me the ip address [x.x.x.x] output that I want.

However, if I query using the golang query

var SliceIP []NfInstance

db.C(COLLECTION).Find(bson.M{
                      "nfType": "AMF",
                      "amfInfo.amfSetId": "3fa85f64-5717-4562-b3fc-2c963f66af33"}
                      ).Distinct("ipv4Addresses", &SliceIP)

I'm getting an empty array instead of the the IP address string in an array. In the database i have the json document as

{
    "nfinstanceID": "3fa85f64-5717-4562-b3fc-2c963f66af33",
    "nfType": [
        "AMF"
    ],
    "nfStatus": [
        "REGISTERED"
    ],
    "sNssais": [
        {
            "sst": 1,
            "sd": "sd1"
        }
    ],
    "nsiList": [
        "string"
    ],
    "ipv4Addresses": [
        "198.51.100.300"
    ],
    "allowedNssais": [
        {
            "sst": 1,
            "sd": "sd1"
        }
    ],
    "amfInfo": {
        "amfSetId": "3fa85f64-5717-4562-b3fc-2c963f66af33",
        "taiList": [
            {
                "plmnId": {
                    "mcc": "244",
                    "mnc": "38"
                },
                "tac": "string"
            }
        ],
        "n2InterfaceAmfInfo": {
            "ipv4EndpointAddress": [
                "198.51.100.105"
            ]
        }
    }
}

Mongodb command line query look like this

> db.nfinstances.distinct("ipv4Addresses",{"nfType":"AMF", "amfInfo.amfSetId": "3fa85f64-5717-4562-b3fc-2c963f66af33"})

mongodb Output:

[ "198.51.100.300" ]

The same output I am expecting using the bson.M

Can anyone help find the problem?

Solution

Query.Distinct() unmarshals the list of distinct values, not complete documents (the equivalent MongoDB query also returns values, not documents).

So simply unmarshal the distinct IPs into a value of type []string (and also never forget about handling errors):

var ips []string

err := db.C(COLLECTION).Find(bson.M{
    "nfType":           "AMF",
    "amfInfo.amfSetId": "3fa85f64-5717-4562-b3fc-2c963f66af33",
}).Distinct("ipv4Addresses", &ips)
if err != nil {
    // handle error
}