Go like benchmark function for Kotlin

BenchmarkIt.kt

import kotlin.system.measureTimeMillis

fun benchmarkIt(msg: String, block: (Int) -> Unit) {
    var n = 1
    var duration: Long

    do {
        duration = measureTimeMillis { repeat(n, block) }
        n *= 2
    } while (duration < 100L)

    val nsPerOp = duration.toDouble() * 1000 / n.toDouble()

    println(
            "%s ran %d operations in %d milliseconds; avg: %.3f ns/op".format(
                    msg, n, duration, nsPerOp
            )
    )
}

// Outputs (on my machine):
// String interpolation ran 8388608 operations in 191 milliseconds; avg: 0.023 ns/op
// String concatenation ran 8388608 operations in 172 milliseconds; avg: 0.021 ns/op
fun main(args: Array<String>) {
    benchmarkIt("String interpolation") {
        "String $it interpolation"
    }

    benchmarkIt("String concatenation") {
        "String " + it + " concatenation"
    }
}