redirect: Cancel async request before redirecting

Closes #372

lib/req/finch.ex

@@ -292,6 +292,16 @@ defmodule Req.Finch do
 
   defp finch_cancel(ref) do
     Finch.cancel_async_request(ref)
+    clean_responses(ref)
+    :ok
+  end
+
+  defp clean_responses(ref) do
+    receive do
+      {^ref, _} -> clean_responses(ref)
+    after
+      0 -> :ok
+    end
   end
 
   defp finch_name(request) do

lib/req/steps.ex

@@ -1691,6 +1691,10 @@ defmodule Req.Steps do
       redirect_count = Req.Request.get_private(request, :req_redirect_count, 0)
 
       if redirect_count < max_redirects do
+        with %Req.Response.Async{} <- response.body do
+          Req.cancel_async_response(response)
+        end
+
         request =
           request
           |> build_redirect_request(response, location)

test/req/finch_test.exs

@@ -401,6 +401,29 @@ defmodule Req.FinchTest do
       assert resp.status == 200
       assert :ok = Req.cancel_async_response(resp)
     end
+
+    @tag :capture_log
+    test "into: :self with redirect" do
+      %{url: url} =
+        TestHelper.start_http_server(fn conn ->
+          Plug.Conn.send_resp(conn, 200, "ok")
+        end)
+
+      %{url: url} =
+        TestHelper.start_http_server(fn conn ->
+          conn
+          |> Plug.Conn.put_resp_header("location", to_string(url))
+          |> Plug.Conn.send_resp(307, "redirecting to #{url}")
+        end)
+
+      req =
+        Req.new(
+          url: url,
+          into: :self
+        )
+
+      assert Req.get!(req).body |> Enum.to_list() == ["ok"]
+    end
   end
 
   describe "pool_options" do