clouddns - enables serving zone data from GCP Cloud
  DNS.
The clouddns plugin is useful for serving zones from
    resource record sets in GCP Cloud DNS. This plugin supports all Google Cloud
    DNS records
    ⟨https://cloud.google.com/dns/docs/overview#supported_dns_record_types⟩.
    This plugin can be used when CoreDNS is deployed on GCP or elsewhere. Note
    that this plugin accesses the resource records through the Google Cloud API.
    For records in a privately hosted zone, it is not necessary to place CoreDNS
    and this plugin in the associated VPC network. In fact the private hosted
    zone could be created without any associated VPC and this plugin could still
    access the resource records under the hosted zone.
clouddns [ZONE:PROJECT_ID:HOSTED_ZONE_NAME...] {
    credentials [FILENAME]
    fallthrough [ZONES...]
}
 
  - ZONE the name of the domain to be accessed. When there are multiple
      zones with overlapping domains (private vs. public hosted zone), CoreDNS
      does the lookup in the given order here. Therefore, for a non-existing
      resource record, SOA response will be from the rightmost zone.
 
  - PROJECT_ID the project ID of the Google Cloud project.
 
  - HOSTED_ZONE_NAME the name of the hosted zone that contains the
      resource record sets to be accessed.
 
  - credentials is used for reading the credential file from
      FILENAME (normally a .json file).
 
  - fallthrough If zone matches and no record can be generated, pass
      request to the next plugin. If [ZONES...] is omitted, then
      fallthrough happens for all zones for which the plugin is authoritative.
      If specific zones are listed (for example in-addr.arpa and
      ip6.arpa), then only queries for those zones will be subject to
      fallthrough.
    
    
  
 
Enable clouddns with implicit GCP credentials and resolve CNAMEs
    via 10.0.0.1:
example.org {
    clouddns example.org.:gcp-example-project:example-zone
    forward . 10.0.0.1
}
 
Enable clouddns with fallthrough:
example.org {
    clouddns example.org.:gcp-example-project:example-zone example.com.:gcp-example-project:example-zone-2 {
        fallthrough example.gov.
    }
}
 
Enable clouddns with multiple hosted zones with the same
  domain:
. {
    clouddns example.org.:gcp-example-project:example-zone example.com.:gcp-example-project:other-example-zone
}