build CoreDNS with a plugin

_.sh

#!/bin/bash

set -e
set -o pipefail
cd "$(dirname $(realpath $0))"
set -x

# update Go
# https://www.vultr.com/docs/install-the-latest-version-of-golang-on-ubuntu
# todo: determine latest version automatically
go_version='1.17.6'
cd /tmp
wget -c "https://golang.org/dl/go$go_version.linux-amd64.tar.gz"
mkdir -p "go$go_version"
tar -C "go$go_version" -xzf "go$go_version.linux-amd64.tar.gz"
rm -r /usr/local/go
mv "go$go_version/go" /usr/local/go
go version

# update coredns
cd ~/coredns
git fetch
latest_tag="$(curl 'https://api.github.com/repos/coredns/coredns/releases/latest' -L -s | jq .tag_name -r)"
git reset --hard "$latest_tag"

# pull ACME plugin
# https://github.com/chinzhiweiblank/coredns-acme/blob/v1.0.2/README.md#getting-started
echo 'acme:github.com/chinzhiweiblank/coredns-acme' >>plugin.cfg
go get github.com/chinzhiweiblank/coredns-acme
go generate
go mod tidy

# build & update coredns
go build
./coredns -version
mv coredns /usr/local/bin/
systemctl restart coredns