@Override protected void doCancel() {
    CompletableFuture<V> maybeFuture = future;
    if (maybeFuture != null) maybeFuture.cancel(true);
  }
Defers I/O until {@link #enqueue(Callback)} or {@link #execute()} are called.
zipkin-storage/cassandra/src/main/java/zipkin2/storage/cassandra/internal/call/ResultSetFutureCall.java