@VisibleForTesting
    CompletableFuture<Void> getAfterReadTryReadaheadCf() {
        return afterReadTryReadaheadCf;
    }
This method is only for unit testing.
AfterReadTryReadaheadCf is empty, the task has been completed
AfterReadTryReadaheadCf is not empty, the task may be completed

@return afterReadTryReadaheadCf
s3stream/src/main/java/com/automq/stream/s3/cache/blockcache/StreamReader.java