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: struct.go
    path of file: ./repos/chatnio/adapter/sparkdesk
    
    the code of the file until where you have to start completion: package sparkdesk

import (
	"chat/globals"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
	"fmt"
	"net/url"
	"strings"
	"time"
)

type ChatInstance struct {
	AppId     strin
    
func TransformModel(model string) string {
	switch model {
	case globals.SparkDesk:
		return "general"
	case globals.SparkDeskV2:
		return "generalv2"
	case globals.SparkDeskV3:
		return "generalv3"
	default:
		return "general"
	}
}