player.ResolveURL() returns "no url could be found"

[cofonseca]

I'm trying to use this library to download audio for a given video. In my case, I already have the video ID as a string, and I am providing it to the Load() method directly: youtube.Load(videoID). A player gets returned, I can use it to get audio, and I can see the filename of each audio track. When I try to use player.ResolveURL() to retrieve the full URL of the audio, it returns an error. I see the same result for every video that I try.

Here's an example code snippet that I've set up to demonstrate:

func getAudioFromVideo(string videoID) {
	player, err := ydl.Load(videoID)
	fmt.Println("Attempting to get audio for ID:", videoID)
	if err != nil {
		fmt.Println("Error with player:", err)
	}	

	stream := player.SourceFormats().AudioOnly().SortByAudioQuality()
	for i, s := range stream {
		fmt.Println("")
		fmt.Println("Attempting to get audio version", i+1, "of", len(stream))
		fmt.Println(s)

		audioOnlyFilename := "audio." + s.FileExtension()
		fmt.Println("audioOnlyFilename:", audioOnlyFilename)

		audioOnlyURL, err := player.ResolveURL(s)
		if err != nil {
			fmt.Println("Error on ResolveURL:", err)
		}
		fmt.Println(audioOnlyURL)
	}
}

getAudioFromVideo("fhCTLEEkhYY")

This code results in the following output: