KtorApplication.kt

fun Application.module() {

    val jsonParser = Json {
        ignoreUnknownKeys = true
        isLenient = true
    }

    install(ContentNegotiation) {
        json(jsonParser)
    }
    val client = HttpClient(Apache) {
        install(JsonFeature) {
            serializer = KotlinxSerializer(jsonParser)
        }
    }
    routing {
        post("/greeting") {
            val greetingRequest = call.receive<GreetingRequest>()
            val ipAddress = client.get<IpAddress>("https://api.ipify.org?format=json")
            call.respond(GreetingResponse("Hello ${greetingRequest.firstName} ${greetingRequest.lastName}", ipAddress.ip))
        }
    }
}

@Serializable
class IpAddress(var ip: String)