@Override
    public String toString() {
        return MoreObjects.toStringHelper(this)
                          .add("originalEndpoint", originalEndpoint)
                          .add("endpoint", endpoint)
                          .add("initializationStarted", initializationStarted())
                          .add("initialized", initialCheckFuture.isDone())
                          .add("destroyed", destroyed)
                          .add("refCnt", refCnt)
                          .toString();
    }
Keeps the {@link Future}s which were scheduled via this {@link ScheduledExecutorService}.
Note that this field is also used as a lock.
core/src/main/java/com/linecorp/armeria/client/endpoint/healthcheck/DefaultHealthCheckerContext.java