Serving static files from Rack

config.ru

root = 'public'

use Rack::Static,
  urls:         Dir["#{root}/*"].map { |file| file.sub(root, '')},
  root:         root,
  index:        'index.html',
  header_rules: [[:all, { 'Cache-Control' => 'public, max-age=3600' }]]

run -> env {
  [
    200,
    {
      'Content-Type'  => 'text/html',
      'Cache-Control' => 'public, max-age=86400'
    },
    File.open("#{root}/index.html", File::RDONLY)
  ]
}