Use API Routes on localhost on build in Next.js

Question

When I'm building my project with npm run build command I get a connection error because there is no API server running.

export const getStaticProps = async () => {

const res = await fetch(`127.0.0.1:3000/api/articles`);
articles = await res.json();  
    return {
      props: {
        articles
             }
           }
}

But it works perfectly with npm run dev. Because there is a server running at 127.0.0.1:3000

I did this workaround (use local data on build):

  if (server !== 'none') {
    const res = await fetch(`${server}/api/articles`);
     articles = await res.json();
  } else {
     const articlesData = await import('../../data');
     articles = articlesData.articles;
  }

But it's not what I want. I want to develop both API routes and the rest of my app in one project, then run it with a simple command npm run start.

Is there a solution to this?

I've tried to run both npm run dev and npm run build on separate terminals. One time it worked, but today I can't repeat it. The build command got stuck on this output:

info - Finalizing page optimization

I think it's because those commands share the same directory - .next in the root of the project and their buildings are conflicting with each other.