fix: no longer hangs application due to the request cache (#821)

* use weak timeout (rather than strong timeout)

* remove process.exit, as it is no longer necessary

example/ffmpeg.js

@@ -82,8 +82,6 @@ ffmpegProcess.on('close', () => {
   // Cleanup
   process.stdout.write('\n\n\n\n');
   clearInterval(progressbarHandle);
-  // Close the programm
-  process.exit(0);
 });
 
 // Link streams

lib/cache.js

@@ -9,7 +9,7 @@ module.exports = class Cache extends Map {
       clearTimeout(super.get(key).tid);
     }
     super.set(key, {
-      tid: setTimeout(this.delete.bind(this, key), this.timeout),
+      tid: setTimeout(this.delete.bind(this, key), this.timeout).unref(),
       value,
     });
   }