fix issue 2092

Issue: #2092

Author: JajaComp

servers/graphql-kotlin-server/src/main/kotlin/com/expediagroup/graphql/server/execution/subscription/GraphQLWebSocketServer.kt

@@ -36,6 +36,7 @@ import graphql.GraphQLContext
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.FlowPreview
 import kotlinx.coroutines.Job
+import kotlinx.coroutines.job
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.coroutineScope
 import kotlinx.coroutines.delay
@@ -82,6 +83,10 @@ abstract class GraphQLWebSocketServer<Session, Message>(
                 closeSession(session, GraphQLSubscriptionStatus.CONNECTION_INIT_TIMEOUT)
             }
         }
+        
+        (session as? CoroutineScope)?.coroutineContext?.job?.invokeOnCompletion {
+            subscriptions.values.forEach(Job::cancel)
+        }
 
         requestParser.parseRequestFlow(session)
             .map { objectMapper.readValue<GraphQLSubscriptionMessage>(it) }