I’m walking through this guide, but I get error:
error - TypeError: resolver is not a function
in the following code:

import { openai } from '@ai-sdk/openai';
import { StreamingTextResponse, streamText } from 'ai';

export async function POST(req: Request) {
  try {
    const { messages } = await req.json();

    const result = await streamText({
      model: openai('gpt-4-turbo'),
      messages,
    });

    return new StreamingTextResponse(result.toAIStream());
  } catch (error) {
    console.log(error);
  }
}

Front end code:

'use client';

import React from 'react';
import { useChat } from 'ai/react';

export default function Chatbot() {
  const { messages, input, handleInputChange, handleSubmit } = useChat();
  return (
    <div>
      {messages.map((m) => (
        <div key={m.id} className="whitespace-pre-wrap">
          {m.role === 'user' ? 'User: ' : 'AI: '}
          {m.content}
        </div>
      ))}

      <form onSubmit={handleSubmit}>
        <input
          value={input}
          placeholder="Say something..."
          onChange={handleInputChange}
        />
      </form>
    </div>
  );
}

I’ve tried adding default after export (export default async function...) and then I got this error which I can’t fix:
TypeError: req.json is not a function