Replace Json key in Karate [duplicate]

Question

I need to send a Json to an endpoint but I need to replace a key with a variable.

I've this code

 .....  

  * def idJson = response.id

  Given path <mypath>
  And headers {Authorization: '#(auth)'}
  And request read('classpath:myjson.json')
  .....

The myjson.json file is

{ "a": { ... "b":false, "c":true }, "d": { '#(idJson)': { "Key":[ ..... ] } } }

But the value is not replace in the json. When I perform the request I see that the json contains the string '#(idJson)' instead of the value of the variable. Any idea about how to solve this?

Thank you