You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: api_getChannelTopicSubjectField.go
    path of file: ./repos/databag/net/server/internal
    
    the code of the file until where you have to start completion: package databag

import (
	"bytes"
	"databag/internal/store"
	"encoding/base64"
	"errors"
	"github.com/gorilla/mux"
	"github.com/valyala/fastjson"
	"gorm.io/gorm"
	"net/http"
	"strings"
	"time"
)

//GetChannelTopicSubjectField base64 decodes and downloads a channel topic subject attribute
func GetChannelTopicSubjectField(w http.ResponseWriter, r *http.Request) {

	// scan parameters
	params := mux.Vars(r)
	topicID := params["topicID"]
	field := params["field"]
	elements := strings.Split(field, ".")

	channelSlot, _, code, err := getChannelSlot(r, false)
	if err != nil {
		ErrResponse(w, code, err)
		return
	}

	// load topic
	var topicSlot store.TopicSlot
	if err = store.DB.Where("channel_id = ? AND to
    
func GetChannelTopicSubjectField(w http.ResponseWriter, r *http.Request) {

	// scan parameters
	params := mux.Vars(r)
	topicID := params["topicID"]
	field := params["field"]
	elements := strings.Split(field, ".")

	channelSlot, _, code, err := getChannelSlot(r, false)
	if err != nil {
		ErrResponse(w, code, err)
		return
	}

	// load topic
	var topicSlot store.TopicSlot
	if err = store.DB.Where("channel_id = ? AND topic_slot_id = ?", channelSlot.Channel.ID, topicID).First(&topicSlot).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			code = http.StatusNotFound
		} else {
			code = http.StatusInternalServerError
		}
		ErrResponse(w, code, err)
		return
	}
	if topicSlot.Topic == nil {
		ErrResponse(w, http.StatusNotFound, errors.New("referenced missing topic"))
		return
	}

	// decode data
	strData := fastjson.GetString([]byte(topicSlot.Topic.Data), elements...)
	binData, err := base64.StdEncoding.DecodeString(strData)
	if err != nil {
		ErrResponse(w, http.StatusNotFound, err)
		return
	}

	// response with content
	http.ServeContent(w, r, field, time.Unix(topicSlot.Topic.Updated, 0), bytes.NewReader(binData))
}