Dgraph4j Not found extra exception log

I got the follow log , but there is no extra detail for exception reason , the detail was lost

java.lang.RuntimeException: java.util.concurrent.CompletionException: java.lang.RuntimeException: The doRequest encountered an execution exception:

environment:
jdk 11, kotlin
dgraph4j v21.12.0
dgraph version 23

Maybe it’s because the connection was disconnected。