actions: add go 1.21 to testing set #359

	name: Go
	on: [push]
	jobs:
	build:
	name: Build
	runs-on: ${{ matrix.os }}
	strategy:
	matrix:
	os: [macos-latest, ubuntu-latest]
	goversion: [1.19, "1.20", "1.21"]
	steps:
	- name: Set up Go ${{matrix.goversion}} on ${{matrix.os}}
	uses: actions/setup-go@v3
	with:
	go-version: ${{matrix.goversion}}
	id: go

	- name: Check out code into the Go module directory
	uses: actions/checkout@v2

	- name: gofmt
	run: \|
	[[ -z $(gofmt -l $(find . -name '*.go') ) ]]

	- name: Get dependencies
	env:
	GO111MODULE: on
	run: go mod download

	- name: Vet
	env:
	GO111MODULE: on
	run: go vet -mod=readonly ./...

	- name: Test
	env:
	GO111MODULE: on
	run: go test -mod=readonly -v -count 2 ./...

	- name: Race Test
	env:
	GO111MODULE: on
	run: go test -race -mod=readonly -v -count 2 ./...

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