dig with 169.254.169.254
$ gcloud app deploy app.yaml
$ curl https://<GAE_URL>/dns-check?url=<URL>
Example:
$ curl "https://<GCP_PROJECT_ID>.uc.r.appspot.com/dns-check?url=speech.googleapis.com"
URL: speech.googleapis.com
IP: 64.233.183.95 Times: 5
IP: 74.125.126.95 Times: 7
IP: 173.194.74.95 Times: 9
IP: 74.125.129.95 Times: 5
IP: 173.194.198.95 Times: 5
IP: 74.125.69.95 Times: 15
IP: 74.125.124.95 Times: 19
IP: 173.194.197.95 Times: 11
IP: 209.85.146.95 Times: 2
IP: 74.125.202.95 Times: 7
IP: 172.253.119.95 Times: 4
IP: 173.194.192.95 Times: 2
IP: 173.194.195.95 Times: 2
IP: 173.194.193.95 Times: 2
IP: 74.125.70.95 Times: 4
IP: 172.253.114.95 Times: 6
IP: 209.85.147.95 Times: 5
IP: 74.125.201.95 Times: 2
IP: 209.85.145.95 Times: 2
IP: 64.233.181.95 Times: 3
IP: 172.217.214.95 Times: 100
IP: 209.85.234.95 Times: 8
IP: 209.85.200.95 Times: 18
IP: 64.233.191.95 Times: 3
IP: 142.250.1.95 Times: 1
IP: 108.177.112.95 Times: 53
IP: 108.177.120.95 Times: 10
IP: 108.177.111.95 Times: 76
IP: 172.217.219.95 Times: 7
IP: 74.125.132.95 Times: 7
IP: 173.194.194.95 Times: 4
IP: 172.217.212.95 Times: 100
IP: 108.177.121.95 Times: 11