Loosely based off this [blog post][http://skarlso.github.io/2016/06/12/google-signin-with-go/] this is an example of how to authenticate with google using Golang and OAuth2.
go get golang.org/x/oauth2 cloud.google.com/go/compute/metadata github.com/gorilla/sessions github.com/gorilla/mux
Go to google developer console and start a new project.
Once in the new project, in the product and services menu select APIs and services then credentials.
Click Create Credentials and OAuth client id.
You will have to set up the details for your web application by giving it a name and setting authorised origins and redirect uris.
These can be changed later but make sure to use http://127.0.0.1:<your_port> instead of localhost.
Once complete you will get a clientID and clientSecret. Fill out these values in the creds.json file in the main directory.
Once these are in place, run the application with the command: go run main.go.