Add support for go 1.21 #49

	name: build
	on: [push]

	jobs:
	build:
	strategy:
	matrix:
	go-version: ['1.15', '1.16', '1.17', '1.18', '1.19', '1.20', '1.21']
	os: [ubuntu-latest, macos-latest]
	runs-on: ${{ matrix.os }}
	steps:
	- name: Set up Go
	uses: actions/setup-go@v2
	with:
	go-version: ${{ matrix.go-version }}

	- name: Checkout code
	uses: actions/checkout@v2

	- name: Build
	run: \|
	GOOS=freebsd go build
	GOOS=windows go build
	GOOS=openbsd go build
	go build -v .

	- name: Test
	run: \|
	go vet
	go test -v -race -coverprofile=coverage.txt -covermode=atomic

	- name: After success
	run: \|
	bash <(curl -s https://codecov.io/bash)

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