Fix gstreamer-send

Block until ICE Gathering is complete. Otherwise the returned SDP will
not have any ICE candidates.

Author: oasangqi

README.md

@@ -73,6 +73,7 @@ Check out the **[contributing wiki](https://github.com/pion/webrtc/wiki/Contribu
 * [Pascal Benoit](https://github.com/pascal-ace)
 * [Jin Gong](https://github.com/cgojin)
 * [harkirat singh](https://github.com/hkirat)
+* [oasangqi](https://github.com/oasangqi)
 
 ### License
 MIT License - see [LICENSE](LICENSE) for full text

gstreamer-send/main.go

@@ -84,12 +84,17 @@ func main() {
 		panic(err)
 	}
 
+	// Create channel that is blocked until ICE Gathering is complete
+	gatherComplete := webrtc.GatheringCompletePromise(peerConnection)
+
 	// Sets the LocalDescription, and starts our UDP listeners
 	err = peerConnection.SetLocalDescription(answer)
 	if err != nil {
 		panic(err)
 	}
 
+	<-gatherComplete
+
 	// Output the answer in base64 so we can paste it in browser
 	fmt.Println(signal.Encode(*peerConnection.LocalDescription()))