You will first need to create a GCE instance and then provide details of this instance as below.
export GOOGLE_APPLICATION_CREDENTIALS=<path-to-service-account-json-file>
export GCE_INSTANCE_NAME=<gce-instance-name>
export GCE_INSTANCE_ZONE=<gce-instance-zone>
export GCE_INSTANCE_PROJECT=<gce-project-name>
go test
To get path-to-service-account-json-file
Go to GCE console -> Compute Engine -> VM Instances -> <your-instance>
Find the service account used for this instance in the "Service Account" section
Go to GCE console -> IAM & admin -> Service Accounts -> <instance-service-account>
Select "Create key" and download the .json file
Set GOOGLE_APPLICATION_CREDENTIALS to the path of the .json file