Add CI build job targeting the same Go version as listed in this project's go.mod file

[atc0005]

The current version listed in the go.mod file is Go 1.14:

go-teams-notify/go.mod

Lines 9 to 11 in cc08182

	module github.com/atc0005/go-teams-notify/v2
	go 1.14

Yet as I write this, we're currently building/linting/testing using the most recent stable version of Go (1.20.2) and the most recent oldstable version of Go (1.19.7).

The original maintainer added their go.mod file in 2020 when Go modules support was still fairly new and around the time that Go 1.14 was first released (2020-02-25).

This project still lists support for Go 1.14 (and doesn't use newer Go features) since the assumption is that library consumers still need to build using older Go versions. This is likely a false assumption.

Until an audit can be performed to confirm one way or the other, we should add a separate CI build/test job using the last available Go version from the series referenced by the go.mod file.

Depending on what this project's dependencies require (currently stretchr/testify), we may be forced to re-evaluate the minimum Go version supported.

[atc0005]

See also:

• https://github.com/atc0005/go-ci/pkgs/container/go-ci/72091561?tag=go-ci-mirror-build-go1.14