chore: apply good idea from francis

instrumentation/rack/lib/opentelemetry/instrumentation/rack/middlewares/event_handler.rb

@@ -53,13 +53,12 @@ class EventHandler
           # @param [Rack::Response] This is nil in practice
           # @return [void]
           def on_start(request, _)
-            if untraced_request?(request.env)
-              ctx = OpenTelemetry::Common::Utilities.untraced
-              request.env[UNTRACED_CTX_TOKEN] = OpenTelemetry::Context.attach(ctx)
-              return
-            end
+            parent_context = if untraced_request?(request.env)
+                               extract_remote_context(request, OpenTelemetry::Common::Utilities.untraced)
+                             else
+                               extract_remote_context(request)
+                             end
 
-            parent_context = extract_remote_context(request)
             span = create_span(parent_context, request)
             span_ctx = OpenTelemetry::Trace.context_with_span(span, parent_context: parent_context)
             rack_ctx = OpenTelemetry::Instrumentation::Rack.context_with_span(span, parent_context: span_ctx)
@@ -178,9 +177,10 @@ def create_request_span_name(request)
             end
           end
 
-          def extract_remote_context(request)
+          def extract_remote_context(request, context = Context.current)
             OpenTelemetry.propagation.extract(
               request.env,
+              context: context,
               getter: OpenTelemetry::Common::Propagation.rack_env_getter
             )
           end
@@ -199,10 +199,7 @@ def request_span_attributes(env)
           end
 
           def detach_context(request)
-            if (untracted_ctx_token = request.env[UNTRACED_CTX_TOKEN])
-              OpenTelemetry::Context.detach(untracted_ctx_token)
-              return
-            end
+            return nil unless request.env[OTEL_TOKEN_AND_SPAN]
 
             token, span = request.env[OTEL_TOKEN_AND_SPAN]
             span.finish