feat: option to select model for express

packages/create-llama/questions.ts

@@ -189,7 +189,7 @@ export const askQuestions = async (
     }
   }
 
-  if (program.framework === "nextjs") {
+  if (program.framework === "express" || program.framework === "nextjs") {
     if (!program.model) {
       if (ciInfo.isCI) {
         program.model = getPrefOrDefault("model");

packages/create-llama/templates/index.ts

@@ -176,7 +176,7 @@ const installTSTemplate = async ({
     });
   }
 
-  if (framework === "nextjs") {
+  if (framework === "nextjs" || framework === "express") {
     await fs.writeFile(
       path.join(root, "constants.ts"),
       `export const MODEL = "${model || "gpt-3.5-turbo"}";\n`,

packages/create-llama/templates/types/simple/express/constants.ts

+export const MODEL = "gpt-3.5-turbo";

packages/create-llama/templates/types/simple/express/src/controllers/chat.controller.ts

 import { NextFunction, Request, Response } from "express";
 import { ChatMessage, OpenAI } from "llamaindex";
+import { MODEL } from "../../constants";
 import { createChatEngine } from "./engine";
 
 export const chat = async (req: Request, res: Response, next: NextFunction) => {
@@ -14,7 +15,7 @@ export const chat = async (req: Request, res: Response, next: NextFunction) => {
     }
 
     const llm = new OpenAI({
-      model: "gpt-3.5-turbo",
+      model: MODEL,
     });
 
     const chatEngine = await createChatEngine(llm);

packages/create-llama/templates/types/streaming/express/constants.ts

+export const MODEL = "gpt-3.5-turbo";

packages/create-llama/templates/types/streaming/express/src/controllers/chat.controller.ts

 import { streamToResponse } from "ai";
 import { NextFunction, Request, Response } from "express";
 import { ChatMessage, OpenAI } from "llamaindex";
+import { MODEL } from "../../constants";
 import { createChatEngine } from "./engine";
 import { LlamaIndexStream } from "./llamaindex-stream";
 
@@ -16,7 +17,7 @@ export const chat = async (req: Request, res: Response, next: NextFunction) => {
     }
 
     const llm = new OpenAI({
-      model: "gpt-3.5-turbo",
+      model: MODEL,
     });
 
     const chatEngine = await createChatEngine(llm);