core/src/main/java/org/trimou/engine/segment/AsyncAppendable.java
private void flush() {
        try {
            parent.append(future.get(60, TimeUnit.SECONDS).collect(this));
            parent.append(buffer);
            if (parent instanceof AsyncAppendable) {
                ((AsyncAppendable) parent).flush();
            }
        } catch (Exception e) {
            throw new MustacheException(
                    MustacheProblem.RENDER_ASYNC_PROCESSING_ERROR, e);
        }
    }
private void flush() {
        try {
            parent.append(future.get(60, TimeUnit.SECONDS).collect(this));
            parent.append(buffer);
            if (parent instanceof AsyncAppendable) {
                ((AsyncAppendable) parent).flush();
            }
        } catch (Exception e) {
            throw new MustacheException(
                    MustacheProblem.RENDER_ASYNC_PROCESSING_ERROR, e);
        }
    }
Append the result to the parent.