net/http: close response body in TestRequestBodyLimit

Failing to close the response body before returning leaks
the in-progress request past the test lifetime.

Fixes #60264

Change-Id: Ic327d9f8e02e87ed656324aaa042f833d9ea18ca
Reviewed-on: https://go-review.googlesource.com/c/go/+/501309
Run-TryBot: Damien Neil <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Bryan Mills <[email protected]>

Author: neild

src/net/http/serve_test.go

@@ -3012,7 +3012,10 @@ func testRequestBodyLimit(t *testing.T, mode testMode) {
 	//
 	// But that's okay, since what we're really testing is that
 	// the remote side hung up on us before we wrote too much.
-	_, _ = cst.c.Do(req)
+	resp, err := cst.c.Do(req)
+	if err == nil {
+		resp.Body.Close()
+	}
 
 	if atomic.LoadInt64(nWritten) > limit*100 {
 		t.Errorf("handler restricted the request body to %d bytes, but client managed to write %d",