Throughout the book, we have written many suspending algorithms, but most of the time it has been done using coroutine builders such as launch(), async(), and runBlocking(). When calling a coroutine builder, the code that we pass to it is a suspending lambda. Now it's time to take a detailed look at how to write suspending code that exists as a function instead:
suspend fun greetDelayed(delayMillis: Int) {
delay(delayMillis)
println("Hello, World!")
}
To create a suspending function, you only need to add the modifier suspend to its signature. Notice that suspending functions can call other suspending functions such as delay() directly – no need to wrap inside a coroutine builder– making our code clean and easy to read.
Nevertheless, if we try calling this function outside of a coroutine it will not work. Consider this example...
