Hello. In the project next.js I have a file counter.ts:

export let counter: number = 0;

export function increment(n: number): void {
  counter += n;
}

Then I use increment function in api route /api/test/test1:

increment(5);
console.log('1', counter);

Then get counter 5. But in api/test/test2 I use this code:

console.log('2', counter);

First time I open api route /api/test/test1 and get the counter: 5 in console.log. Then I open /api/test/test2 and get the counter: 0;

What is problem? How can I synchronize counter between two routes?