Add ability to use multiple instances of middleware

lib/rack/attack.rb

@@ -96,9 +96,16 @@ def reset!
 
     attr_reader :configuration
 
-    def initialize(app)
+    def initialize(app, &block)
       @app = app
-      @configuration = self.class.configuration
+      @configuration =
+        if block_given?
+          configuration = Configuration.new
+          configuration.instance_exec(&block)
+          configuration
+        else
+          self.class.configuration
+        end
     end
 
     def call(env)

spec/acceptance/rails_middleware_spec.rb

@@ -16,5 +16,17 @@
       @app.initialize!
       assert @app.middleware.include?(Rack::Attack)
     end
+
+    it "can be configured via a block" do
+      @app.middleware.delete(Rack::Attack)
+      @app.middleware.use(Rack::Attack) do
+        blocklist_ip("1.2.3.4")
+      end
+      get "/", {}, "REMOTE_ADDR" => "1.2.3.4"
+      assert_equal 403, last_response.status
+
+      get "/", {}, "REMOTE_ADDR" => "4.3.2.1"
+      assert_equal 200, last_response.status
+    end
   end
 end