使用正则表达式在过滤器中返回多个值

Question

我有一个 JSON 文件，每条记录都遵循这样的格式，其中包含世界各地各个城市的名称。

{
    "_id": {
        "$oid": "5f856f2ee2d00c1818791982"
    },
    "name": "Sant Julia de Loria",
    "all_names": "Sant Julià de Lòria, Sant Julia de Loria, San Julia,San Julià,Sant Julia de Loria,Sant Julià de Lòria,Sant-Zhulija-de-Lorija,sheng hu li ya-de luo li ya,Сант-Жулия-де-Лория,サン・ジュリア・デ・ロリア教区,圣胡利娅-德洛里亚,圣胡利娅－德洛里亚",
    "alternate_names": "San Julia,San Julià,Sant Julia de Loria,Sant Julià de Lòria,Sant-Zhulija-de-Lorija,sheng hu li ya-de luo li ya,Сант-Жулия-де-Лория,サン・ジュリア・デ・ロリア教区,圣胡利娅-德洛里亚,圣胡利娅－德洛里亚",
    "country_code": "AD",
    "country_name": "Andorra"
}

我的应用程序在通过 URL 参数查询时基本上会返回城市名称。这应该通过正则表达式过滤器，然后在 JSON 中搜索适当的城市名称。

func searchCity(w http.ResponseWriter, r *http.Request) { // GET request that takes in a url param and returns a list of cities from the DB
    w.Header().Set("Content-Type", "application/json")

    values := r.URL.Query()
    city := values["city_name"]                                                               // Assigns url param from route `/suggest?city_name=` to 'city'
    cityCollection := client.Database(os.Getenv("CITY_DB")).Collection(os.Getenv("COL_CITY")) // Holds 'city' collection from DB

    if len(city) == 0 {
        w.WriteHeader(http.StatusOK)
        w.Write([]byte(`{"Error": "City name cannot be empty!"}`))
        return
    }

    filter := bson.D{ //Regex filter for querying the input through the DB
        primitive.E{
            Key: "all_names", Value: primitive.Regex{
                Pattern: city[0], Options: "i",
            },
        },
    }

    cursor, err := cityCollection.Find(r.Context(), filter) // Query to find city is declared with cursor
    if err != nil {
        log.Fatal(err)
        w.WriteHeader(http.StatusInternalServerError)
        w.Write([]byte(`{"Error": "Could not execute cursor into query."}`))
        return
    }

    var cityList []City
    for cursor.Next(context.TODO()) { // Runs through each document entry in DB to see if regex matches
        var cities City
        err := cursor.Decode(&cities)
        if err != nil {
            log.Fatal(err)
            w.WriteHeader(http.StatusInternalServerError)
            w.Write([]byte(`{"Error": "Could not run cursor."}`))
            return
        }
        cityList = append(cityList, cities) // List of cities is appended to cityList
    }
    w.WriteHeader(http.StatusOK)
    if len(cityList) == 0 {
        w.Write([]byte(`{"cities": []}`))
        return
    }
    json.NewEncoder(w).Encode(cityList)

}

用于创建 cityList 对象的 City 类型模型包含正确的值。

type City struct {
    Name    string `bson:"name" json:"name"`
    Country string `bson:"country" json:"country"`
}

我一直在尝试返回 country_name 以及城市名称，但我不知道如何将其正确写入过滤器。