feat: flow example 추가

src/main/kotlin/com/huisam/kotlincoroutine/flow/Flow.kt

@@ -0,0 +1,44 @@
+package com.huisam.kotlincoroutine.flow
+
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.flow.collectLatest
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.onStart
+import kotlinx.coroutines.runBlocking
+import java.util.concurrent.atomic.AtomicLong
+
+fun main(): Unit = runBlocking(Dispatchers.Default) {
+    val flowStartTime = AtomicLong(0L)
+
+    flow {
+        repeat(times = 3) { data ->
+            delay(300L)
+            produceLog(flowStartTime.get(), data)
+            emit(data)
+        }
+    }.onStart {
+        flowStartTime.set(System.currentTimeMillis())
+    }.collectLatest { data ->
+        delay(700L)
+        consumerLog(flowStartTime.get(), data)
+    }
+}
+
+private fun produceLog(flowStartTime: Long, data: Int) {
+    println(
+        """
+            Time: ${elapsedFromStartTime(flowStartTime)}ms / Producer Coroutine : ${Thread.currentThread().name} / data : $data [>>]
+        """.trimIndent()
+    )
+}
+
+private fun consumerLog(flowStartTime: Long, data: Int) {
+    println(
+        """
+            Time: ${elapsedFromStartTime(flowStartTime)}ms / Consumer Coroutine : ${Thread.currentThread().name} / data : $data [<<]
+        """.trimIndent()
+    )
+}
+
+private fun elapsedFromStartTime(flowStartTime: Long) = System.currentTimeMillis() - flowStartTime