How to use "Use video" / "choose" button from video in swift 3? - ios

Question

I'm trying to upload my video chosen from library or recorded from camera to firebase. When I get the video from library there's a "choose" button on the image picker or when I record the video it says "Use video".
I think to run those buttons function you have to write the didFinishPickingMediaWithInfo function. But nothing happens when I record a video and click "choose" this is what I have as my code:
if (UIImagePickerController.isSourceTypeAvailable(.camera)) {
if UIImagePickerController.availableCaptureModes(for: .rear) != nil {
//if the camera is available, and if the rear camera is available, the let the image picker do this
imagePicker.sourceType = .camera
imagePicker.mediaTypes = [kUTTypeMovie as String]
imagePicker.allowsEditing = false
imagePicker.delegate = self as? UIImagePickerControllerDelegate & UINavigationControllerDelegate
imagePicker.videoMaximumDuration = 60
imagePicker.videoQuality = .typeIFrame1280x720
present(imagePicker, animated: true, completion: nil)
} else {
postAlert("Rear camera doesn't exist", message: "Application cannot access the camera.")
}
} else {
postAlert("Camera inaccessable", message: "Application cannot access the camera.")
}
}
func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
print("didFinishPickingMediaWithInfo")
}
I want it to at least print to know that the video "choose button" is working. Any ideas on how to get the choose button to work? Any help would be kind. Thank you in advance!