@Override
        public void onDrainEnd(ChannelHandlerContext ctx) throws Exception {
            Http2ServerConnectionHandler.super.close(ctx, ctx.newPromise());
            // Cancel scheduled tasks after the call to the super class above to avoid triggering
            // needsImmediateDisconnection.
            cancelScheduledTasks();
        }
Start channel shutdown. Will send final GOAWAY with latest created stream ID.
core/src/main/java/com/linecorp/armeria/server/Http2ServerConnectionHandler.java