Having a Body in a Get Request. RestTemplate


so I am making a request to elasticSearch and I want to filter the data received by Timestamp value, I want every data between 6 and 8 A.M. for example. In postman the Body -> raw is something like this:

"query": { 
    "bool": { 
      "filter": [ 
        { "range": { "timestamp": { "gte": "2019-08- 09T06:00:00","lt":"2019-08-09T07:00:00"}}} 

In kotlin I am trying the next piece of code but it doesn’t work. What do I have to change in order to work out? Thanks!

        val forEntity_Flow = restTemplate.exchange("https://X.X.X.X:6200/bla_bla-$da/_search/?size=50&pretty=1",
            HttpMethod.GET, HttpEntity("{\"query\":{\"bool\":{\"filter\":[{\"range\":{\"timestamp\":{\"gte\":\"2019-08-09T06:00:00\",\"lt\":\"2019-08-09T08:00:00\"}}}]}}}", headers), ResultsFlow::class.java)