Tail a Google PUB/SUB topic

$ ./tail-pubsub -h
Usage of ./tail-pubsub:
  -batchsize=1: How many messages to get at once
  -project="": Google project-name
  -topic="": PUB/SUB topic name to subscribe to

Credentials can either be derived from a credentials file, or from instance permissions:

• Credentials-file should be '~/.config/gcloud/application_default_credentials.json'
• Alternatively you can use any other file: export GOOGLE_APPLICATION_CREDENTIALS=~/Downloads/credentials-file.json
• Instance permissions required:
  • PubsubScope = "https://www.googleapis.com/auth/pubsub"