Fix await returned wrong result in sequential implementation (#24)

Author: Sergey Mashkov

kotlinx-coroutines-io/common/src/kotlinx/coroutines/io/ByteChannelSequential.kt

@@ -493,7 +493,7 @@ abstract class ByteChannelSequentialBase(initial: IoBuffer, override val autoFlu
         waitingForRead = atLeast
         atLeastNBytesAvailableForRead.await { afterRead() }
         closedCause?.let { throw it }
-        return !isClosedForRead
+        return !isClosedForRead && availableForRead >= atLeast
     }
 
     override fun discard(n: Int): Int {

kotlinx-coroutines-io/common/test/kotlinx/coroutines/io/ByteChannelSmokeTest.kt

@@ -647,6 +647,29 @@ open class ByteChannelSmokeTest : ByteChannelTestBase() {
         }
     }
 
+    @Test
+    fun testReadSuspendSessionAwait() = runTest {
+        launch {
+            expect(2)
+            ch.writeInt(1)
+            ch.flush()
+            expect(3)
+            ch.close()
+        }
+
+        var result: Boolean? = null
+        ch.readSuspendableSession {
+            expect(1)
+            result = await(100000)
+        }
+
+        expect(4)
+        assertEquals(false, result)
+        assertEquals(4, ch.availableForRead)
+        ch.discard(4)
+        finish(5)
+    }
+
     private fun assertEquals(expected: Float, actual: Float) {
         if (abs(expected - actual) > 0.000001f) {
             kotlin.test.assertEquals(expected, actual)