title: switchMap is not cancelling previous HTTP call
body: <p>one of angular service method(http call) created with switchMap operator,so it can reject/cancel the previous rest API calls if new one arrived. it is working fine and make a backend call but it not reject any BE call but it sequentially calling every call and wait for all of BE call to response, it should reject previous calls.</p>
  <p>where I am doing wrong ?</p>
  <p><a href="https://stackblitz.com/edit/angular-rxjs-switchmap-merge-results-multiple-http-reque-yyq7sn?embed=1&amp;file=src/app/app.component.ts" rel="nofollow noreferrer">stackblitz example</a></p>
  <p>to create first observer event I am using from() method and by each typing it calls HTTP get API.</p>
  <p><a href="https://i.stack.imgur.com/qVJ2P.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qVJ2P.png" alt="enter image description here" /></a></p>