exitProcess

Terminates the currently running process.

inline fun exitProcess(status: Int): Nothing(source)
import kotlin.system.exitProcess

fun main() {
    println("Starting the program.")
    val shouldExit = true
    if (shouldExit) {
        println("Exiting now with status 0.")
        exitProcess(0)
    }
    println("This line will not be reached.")
}

Source