Is go not a first class language for Pulumi? On the getting started there's only TypeScript, JavaScript and Python

Go support is in preview, but is in use by many current users for a core set of scenarios. See also https://www.pulumi.com/docs/intro/languages/.

If I wanted to use Go, where would I need to start? Assuming no knowledge of Pulumi

Here's an example that's a good getting started point: https://github.com/pulumi/examples/tree/master/aws-go-s3-folder