chore(ci): update golang toolchain to 1.21 #169

	# Copyright 2020-present Montgomery Edwards⁴⁴⁸ (github.com/x448).
	# This file is licensed under the MIT License. See LICENSE at https://github.com/x448/workflows for the full text.
	#
	# CI Go Cover 2020.1.28.
	# This GitHub Actions workflow checks if Go (Golang) code coverage satisfies the required minimum.
	# The required minimum is specified in the workflow name to keep badge.svg and verified minimum in sync.
	#
	# To help protect your privacy, this workflow avoids external services.
	# This workflow simply runs `go test -short -cover` --> grep --> python.
	# The python script is embedded and readable in this file.
	#
	# Steps to install and set minimum required coverage:
	# 0. Copy this file to github.com/OWNER_NAME/REPO_NAME/.github/workflows/ci-go-cover.yml
	# 1. Change workflow name from "cover 100%" to "cover ≥92.5%". Script will automatically use 92.5%.
	# 2. Update README.md to use the new path to badge.svg because the path includes the workflow name.

	name: cover ≥77.0%
	on: [push, pull_request]
	jobs:
	cover:
	name: Coverage
	runs-on: ubuntu-latest
	env:
	GO111MODULE: on
	steps:
	- uses: actions/setup-go@v3
	with:
	go-version: "1.21"
	- name: Checkout code
	uses: actions/checkout@v2
	- name: Go Coverage
	run: \|
	go version
	make test-cover \| grep -o "coverage:.*of statements$" \| python scripts/cov.py
	shell: bash

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