Our first option is to use a different context for our update operation:

import kotlinx.coroutines.experimental.*

fun main(args: Array<String>) = runBlocking {
   var counter = 0

   val counterContext = newSingleThreadContext("CounterContext")

   val time = measureTimeMillis {
      repeatInParallel(1_000_000) {
         withContext(counterContext) {
            counter++
         }
      }
   }
   println("counter = $counter")
   println("time = $time")
}

The withContext function executes a block in a specific coroutine context—in this case, a single-threaded one. Switching context is a powerful technique that lets us manipulate, in a fine-grained way, how our code runs.