LaunchBuilder.kt

import kotlin.coroutines.Continuation
import kotlin.coroutines.CoroutineContext
import kotlin.coroutines.EmptyCoroutineContext
import kotlin.coroutines.intrinsics.createCoroutineUnintercepted

fun launch(block: suspend () -> Unit) {
    val callback = object : Continuation<Unit> {  
        override val context: CoroutineContext = EmptyCoroutineContext  
        override fun resumeWith(result: Result<Unit>) {}  
    }  
    block.createCoroutineUnintercepted(callback).resumeWith(Result.success(Unit))
}

fun main(){
    launch{
        greet()
    }
}

suspend fun greet(){
    println("Hello World!")
}