Next.jsデータ取得完全ガイド4：fetchのカスタマイズとRoute Handler

const res = await fetch('https://api.example.com/data', {
  headers: {
    'Authorization': 'Bearer my-token',
  },
});

import { cookies } from 'next/headers';
 
const cookieStore = cookies();
const token = cookieStore.get('token');
const res = await fetch('https://api.example.com/user', {
  headers: {
    Authorization: `Bearer ${token?.value}`,
  },
});

await fetch('https://api.example.com/data', {
  next: {
    tags: ['data'],
  },
});

'use server';
import { revalidateTag } from 'next/cache';
export async function updateSomething() {
  // 데이터 수정 로직
  await revalidateTag('data'); // 'data' 태그에 해당하는 fetch 캐시 무효화
}

// app/api/user/route.ts
import { NextResponse } from 'next/server';
export async function GET() {
  const res = await fetch('https://jsonplaceholder.typicode.com/users/1');
  const user = await res.json();
    return NextResponse.json(user);
}