Let recorder worker close encoder stdin

recording/recorder.go

@@ -128,10 +128,9 @@ func (r *Recorder) Stop() error {
 		return nil
 	}
 	r.once.Do(func() {
+		// run owns stdin and closes it only after it has stopped writing.
+		// Closing it here races writePCM and turns a normal stop into EPIPE.
 		close(r.stop)
-		if r.stdin != nil {
-			r.stdin.Close()
-		}
 	})
 	select {
 	case <-r.done: