next.js/examples/with-segment-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>
)