fun toDns(vararg asyncDns: AsyncDns): Dns =
      Dns { hostname ->
        val allAddresses = mutableListOf<InetAddress>()
        val allExceptions = mutableListOf<IOException>()
        val latch = CountDownLatch(asyncDns.size)

        asyncDns.forEach {
          it.query(
            hostname,
            object : Callback {
              override fun onResponse(
                hostname: String,