dsl.scala

...//set up protocols

val action = send(msg) //here goes our dsl
  .via(/*put here producer*/)
  .receive(/*put here consumer*/)

val scn = scenario("custom plugin") //here goes gatling
  .feeder(feed)
  .exec(action)

setUp(
  scn.inject(atOnceUsers(1))
).protocols(...,...)