I am trying to get list of videos uploaded on my YouTube channel using following
https://www.googleapis.com/youtube/v3/search?part=snippet&channelId{MY_CHANNEL_
Without looking at your API Console settings, I cannot say for sure. But from looking at the HTTP response, it looks like your IP address might be blocked by the Google authorization server. Hence, it is sending you back an unauthorized request HTTP status code 403.
Go to your API Console and select the None radio button from under the Key restrictions section. Then try again. It should work.