Need some examples of dispatch-nio to make several Http requests

Question

I m using dispatch-nio library to make several Http request calls. But I cannot find an example how to handle callback responses through nio library.

And also I am unable to handle exceptions thrown by nio.Http call. Could anyone please post an example or an url where we can find some information of it.

So far I achieved:

    val http = new nio.Http
    withShutdown(http) {

    val host = :/("http://example.org") /"api"
    val withParams = host <<? Map(      
      "page" -> "1"
    )
      val future = http(withParams as_str)

       while (!future.isSet) { 
          println("Waiting for results...")
          Thread.sleep(15000)
       }

      future.apply()
    }

  }

How to set headers and onComplete? any example please

Thanks in advance.