@Override
        public Response execute() throws IOException {
            final CompletableCallback completableCallback = new CompletableCallback();
            enqueue(completableCallback);
            try {
                return completableCallback.join();
            } catch (CancellationException e) {
                throw new IOException(e);
            } catch (CompletionException e) {
                throw new IOException(Exceptions.peel(e));
            }
        }
A {@link Factory} that creates a {@link Call} instance for {@link WebClient}.
retrofit2/src/main/java/com/linecorp/armeria/client/retrofit2/ArmeriaCallFactory.java