Update workflow to use go v1.18 #31

	name: Build
	on:
	push:
	jobs:
	run-tests:
	runs-on: ubuntu-latest
	env:
	TEST_RESULTS: "/tmp/test-results"
	steps:
	- name: Setup go
	uses: actions/setup-go@4d34df0c2316fe8122ab82dc22947d607c0c91f9 # v4.0.0
	with:
	go-version: 1.18
	- uses: actions/checkout@8f4b7f84864484a7bf31766abe9204da3cbe65b3 # v3.5.0
	- run: mkdir -p "$TEST_RESULTS"/go-retryablyhttp
	- name: restore_cache
	uses: actions/cache@69d9d449aced6a2ede0bc19182fadc3a0a42d2b0 # v3.2.6
	with:
	key: go-mod-v1-{{ checksum "go.sum" }}
	restore-keys: go-mod-v1-{{ checksum "go.sum" }}
	path: "/go/pkg/mod"
	- run: go mod download
	- name: Run go format
	run: \|-
	files=$(go fmt ./...)
	if [ -n "$files" ]; then
	echo "The following file(s) do not conform to go fmt:"
	echo "$files"
	exit 1
	fi
	- name: Install gotestsum
	run: go get gotest.tools/gotestsum
	- name: Run unit tests
	run: \|-
	PACKAGE_NAMES=$(go list ./...)
	# shellcheck disable=SC2086 # can't quote package list
	gotestsum --junitfile "${TEST_RESULTS}"/go-retryablyhttp/gotestsum-report.xml -- $PACKAGE_NAMES
	- uses: actions/upload-artifact@0b7f8abb1508181956e8e162db84b466c27e18ce # v3.1.2
	with:
	path: "/tmp/test-results"
	- uses: actions/upload-artifact@0b7f8abb1508181956e8e162db84b466c27e18ce # v3.1.2
	with:
	path: "/tmp/test-results"
	permissions:
	contents: read

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