Migrate from Angular 5 to 6

src/app/services/websocket.service.ts

@@ -3,7 +3,7 @@
 
 import { Injectable } from '@angular/core';
 import { QueueingSubject } from './queueing-subject';
-import { Observable } from 'rxjs/Observable';
+import { Observable } from 'rxjs';
 import websocketConnect from 'rxjs-websockets';
 import { filter, map, share } from 'rxjs/operators';
 import { WSMessage } from './wsmessage';