Basically I copied the official guide and in my page.tsx file, I fetch an API like this:

async function getData() {
  const res = await fetch("http://localhost:8080/ping");
  // The return value is *not* serialized
  // You can return Date, Map, Set, etc.
  if (!res.ok) {
    // This will activate the closest `error.js` Error Boundary
    throw new Error("Failed to fetch data");
  }
  return res.json();
}

export default async function Home() {
  const data = await getData()
  console.log("Request sent!")
  return (
    <div>
      <div>Hello World! I'm Home Page Start</div>
      {data}
      <div>I'm Home Page End.</div>
    </div>
  );
}

And seems there's problem with JSON parsing when I run npm run build.

Error occurred prerendering page "/". Read more: https://nextjs.org/docs/messages/prerender-error
SyntaxError: Unexpected non-whitespace character after JSON at position 4 (line 1 column 5)
at JSON.parse (<anonymous>)
at parseJSONFromBytes (node:internal/deps/undici/undici:5419:19)
at successSteps (node:internal/deps/undici/undici:5390:27)
at fullyReadBody (node:internal/deps/undici/undici:1501:9)
at async specConsumeBody (node:internal/deps/undici/undici:5399:7)

But after I change res.json() to res.json, it works.