Or even simpler:
```
val f = sentinelClients.map(_.getMasterAddr(master))
val ff = Future.firstCompletedOf(f)
                .map {
                      case Some((ip: String, port: Int)) => initFunction(ip, port)
                      case _ => throw new Exception(s"No such master '$master'")
                }

Await.result(ff, 15 seconds)
```