Rackup file for dynamic requests, then static files, then not found

config.ru

require 'rack'
require 'rack/static'

class App
  def initialize(app)
    @app = app
  end

  def call(env)
    req = Rack::Request.new(env)

    case req.path
    when "/hello"
      [200, {}, ["Hello"]]
    else
      @app.call(env)
    end
  end
end

use App
use Rack::Static
run -> (env) { [404, {}, ["Not found"]] }