title: How to stop a sound action in swift spriteKit
body: <p>i am a swift beginner trying to build a game with a sound in it. i use swift SpriteKit and also AVFoundation as my sound starter. Below is the action i call 
  whenever i want a sound action in the game. The sound (background music) plays 
  alright but just wouldn't stop when the game is over.</p>
  
  <pre><code>self.runAction(SKAction.playSoundFileNamed("Sound/Gameplay.wav", waitForCompletion: false))
  </code></pre>
  
  <p>Can somebody please help me get this issue behind me? thanks.</p>