ThreadLocalDelegate.kt

import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty

fun <T> threadLocal(init: () -> T) = object : ReadWriteProperty<Any?, T> {
    private val internal = object : ThreadLocal<T>() {
        override fun initialValue() = init()
    }

    override fun getValue(thisRef: Any?, property: KProperty<*>): T = internal.get()!!

    override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
        internal.set(value)
    }
}