RSpec Cannot Use Defined Variables in Shared Examples

I'm having trouble using a defined variable for a shared example in RSpec. Here's my test:

RSpec.shared_examples "check user logged in" do |method, action, params|
  it "redirects to the sign in page if the user is not logged in" do
    send(method, action, params)
    expect(response).to redirect_to(signin_url)
  end
end

RSpec.describe UsersController, type: :controller do
  describe "GET #show" do
    let(:user) { FactoryGirl.create(:user) } 
    let!(:show_params) do 
      return { id: user.id }
    end

    context "navigation" do
      include_examples "check user logged in", :get, :show, show_params
    end
  end
end

In the test, I'm checking to make sure the user needs to be logged in before the action can be performed. I am receiving the following error message:

method_missing': show_params is not available on an example group

What do I need to change to make show_params accessible? I've tried using it_behaves_like instead of include_examples with no luck. I've also tried removing the context "navigation" block to no avail. I need to perform this check across multiple controllers and actions, so it seems a shared example might be the correct way to reuse code.