Error in go.mod file in quickstart google cloud platform file

Hi all,
I am trying to deploy the google cloud function for downlink to google pub sub topic using the go function file shown in this link, https://www.chirpstack.io/project/guides/google-cloud-platform/, while deploying the function it is showing error in go.mod file that there is a problem in first line of the file i.e. “module iotpubsub”. According to my knowledge this particular line should be some kind of a link. Can anyone guide me what should be the correct go.mod file to be used here