How to delete elements in an array using RethinkDB

I have a table that Lobbysactually contains party rooms, it has an array of Members and an array of Messages, here is an example:

{
"id":  "a77be9ff-e10f-41c1-8a4c-66b5a55d823c" ,
"members": [
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt" ,
"Gacnt"
] ,
"messages": [ ]
}

Now when the user's websocket connects to Lobbyit, it will add their username to the Memberslist, and I am trying to do this so that when the user leaves Partyit, it is removed from the member list , I came up with this:

r.db("gofinder").table("Lobbys").get("a77be9ff-e10f-41c1-8a4c-66b5a55d823c")("members").update({
  members: r.db("gofinder").table("Lobbys").get("a77be9ff-e10f-41c1-8a4c-66b5a55d823c")("members").ne("Gacnt")
})

But I got the error:

e: Could not prove argument deterministic.  Maybe you want to use the non_atomic flag? in:
r.db("gofinder").table("Lobbys").get("a77be9ff-e10f-41c1-8a4c-66b5a55d823c")("members").update({"members": r.db("gofinder").table("Lobbys").get("a77be9ff-e10f-41c1-8a4c-66b5a55d823c")("members").ne("Gacnt")})
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

But apparently there is a bug, I'm new to Rethink so I'm not sure exactly what to do, unless I should select the array, modify it myself, and put back the new array.

Right now, I'm currently using this solution, but I feel like it might be simpler, especially if I can have it ReQLmodify the array instead of doing it manually

This is my current solution, not related to the problem

query = gorethink.Table("Lobbys").Get(userinfo.LobbyID).Field("members")
res, err := query.Run(db)
if err != nil {
    log.Println(err)
}
defer res.Close()
var members []string
if err = res.All(&members); err != nil {
    log.Println(err)
}

for i := 0; i < len(members); i++ {
    if members[i] == userinfo.Username {
        members = append(members[:i], members[i+1:]...)
        i--
    }
}

query = gorethink.Table("Lobbys").Get(userinfo.LobbyID).Update(map[string]interface{}{
    "members": members,
})