Fix spring websocket adapter's deadlock

Related:
#72

krossbow-websocket-spring/build.gradle.kts

@@ -17,6 +17,10 @@ dependencies {
     // JSR 356 - Java API for WebSocket (reference implementation)
     // Low-level implementation required by Spring's client
     implementation("org.glassfish.tyrus.bundles:tyrus-standalone-client-jdk:1.15")
+
+    implementation(kotlin("test"))
+    implementation(kotlin("test-junit"))
+    testImplementation(project(":krossbow-websocket-test"))
 }
 
 val dokkaJar by tasks.creating(Jar::class) {

krossbow-websocket-spring/src/main/kotlin/org/hildan/krossbow/websocket/spring/SpringWebSocketClient.kt

@@ -1,8 +1,10 @@
 package org.hildan.krossbow.websocket.spring
 
+import kotlinx.coroutines.GlobalScope
 import kotlinx.coroutines.asCoroutineDispatcher
 import kotlinx.coroutines.channels.ReceiveChannel
 import kotlinx.coroutines.future.await
+import kotlinx.coroutines.launch
 import kotlinx.coroutines.runBlocking
 import kotlinx.coroutines.withContext
 import org.hildan.krossbow.websocket.WebSocketFrame
@@ -66,7 +68,12 @@ private class KrossbowToSpringHandlerAdapter : WebSocketHandler {
     }
 
     override fun afterConnectionClosed(session: SpringWebSocketSession, closeStatus: CloseStatus) {
-        runBlocking {
+        // afterConnectionClosed is synchronously called by Tyrus implementation during a session.close() call.
+        // It is not called when receiving the server close frame when the closure is initiated on the client side.
+        // Source: org.glassfish.tyrus.core.ProtocolHandler.close()
+        // This means that if no receiver is listening on the incoming frames channel, onClose() here may suspend
+        // forever. That's why we need an asynchronous dispatch of onClose() here.
+        GlobalScope.launch {
             channelListener.onClose(closeStatus.code, closeStatus.reason)
         }
     }

krossbow-websocket-spring/src/test/kotlin/org/hildan/krossbow/websocket/spring/SpringWebSocketClientTest.kt

@@ -0,0 +1,9 @@
+package org.hildan.krossbow.websocket.spring
+
+import org.hildan.krossbow.websocket.WebSocketClient
+import org.hildan.krossbow.websocket.test.WebSocketClientTestSuite
+
+class SpringWebSocketClientTest : WebSocketClientTestSuite() {
+
+    override fun provideClient(): WebSocketClient = SpringDefaultWebSocketClient
+}

krossbow-websocket-test/src/commonMain/kotlin/org/hildan/krossbow/websocket/test/WebSocketTestUtils.kt

@@ -2,7 +2,7 @@ package org.hildan.krossbow.websocket.test
 
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.ExperimentalCoroutinesApi
-import kotlinx.coroutines.yield
+import kotlinx.coroutines.delay
 import org.hildan.krossbow.websocket.WebSocketClient
 import org.hildan.krossbow.websocket.WebSocketCloseCodes
 import org.hildan.krossbow.websocket.WebSocketFrame
@@ -55,6 +55,6 @@ suspend fun testEchoWs(websocketClient: WebSocketClient, url: String) {
     assertTrue(closeFrame is WebSocketFrame.Close, "Last frame should be a close frame")
     assertEquals(WebSocketCloseCodes.NORMAL_CLOSURE, closeFrame.code)
 
-    yield() // somehow isClosedForReceive needs some time (or at least to regain control)
+    delay(20) // somehow isClosedForReceive needs some time to become true
     assertTrue(session.incomingFrames.isClosedForReceive, "The incoming frames channel should be closed")
 }