build: require Go 1.11 (or higher)

[adamdecaf]

The Terraform project requires Go 1.11 already.

https://github.com/hashicorp/terraform/#developing-terraform

Plus an open PR is failing from such an old Go version.

[adamdecaf]

FYI, I filed a PR for the template also. hashicorp/terraform-provider-template#38

[mildwonkey]

Hi @adamdecaf!
Thank you for submitting this, and I'm sorry for the long silence. The terraform core team has been heads down on 0.12 work for quite a long time at this point. We are upgrading all of the providers we maintain to go 1.11 in an automated fashion, so this PR is no longer needed (#38).
Thanks again for your contribution and I'm sorry again for letting this slide!

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active contributions.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.