next.js/examples/with-google-analytics/components/Header.js

import React from 'react'
import Link from 'next/link'

export default () => (
  <header>
    <nav>
      <ul>
        <li>
          <Link href='/'>
            <a>Home</a>
          </Link>
        </li>
        <li>
          <Link href='/about'>
            <a>About</a>
          </Link>
        </li>
        <li>
          <Link href='/contact'>
            <a>Contact</a>
          </Link>
        </li>
      </ul>
    </nav>
  </header>
)