Thanks @francislavoie & @matt!
Post for future lurkers who might have the similar problem.
Provision a new server, and install Go from scratch:
$ sudo snap install go --classic
$ go version
go version go1.13.8 linux/amd64
Create a new directory and download the main.go file:
$ mkdir -p caddy && cd caddy
$ wget https://raw.githubusercontent.com/caddyserver/caddy/v2/cmd/caddy/main.go
Add the tls.dns module to the main.go file:
// Copyright 2015 Matthew Holt and The Caddy Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package main is the entry point of the Caddy application.
// Most of Caddy's functionality is provided through modules,
// which can be plugged in by adding their import below.
//
// There is no need to modify the Caddy source code to customize your
// builds. You can easily build a custom Caddy with these simple steps:
//
// 1. Copy this file (main.go) into a new folder
// 2. Edit the imports below to include the modules you want plugged in
// 3. Run `go mod init caddy`
// 4. Run `go install` or `go build` - you now have a custom binary!
//
package main
import (
caddycmd "github.com/caddyserver/caddy/v2/cmd"
// plug in Caddy modules here
_ "github.com/caddyserver/caddy/v2/modules/standard"
_ "github.com/caddyserver/tls.dns/providers/cloudflare"
)
func main() {
caddycmd.Main()
}
Finish the build:
$ go mod init caddy
$ go get github.com/caddyserver/caddy/v2@v2.0.0-beta.14
$ go build
Here’s what output from ./caddy list-modules should look like:
caddy.logging.encoders.console
caddy.logging.encoders.filter
caddy.logging.encoders.filter.delete
caddy.logging.encoders.filter.ip_mask
caddy.logging.encoders.json
caddy.logging.encoders.logfmt
caddy.logging.encoders.string
caddy.logging.writers.discard
caddy.logging.writers.file
caddy.logging.writers.net
caddy.logging.writers.stderr
caddy.logging.writers.stdout
caddy.storage.file_system
http
http.authentication.hashes.bcrypt
http.authentication.hashes.scrypt
http.authentication.providers.http_basic
http.encoders.brotli
http.encoders.gzip
http.encoders.zstd
http.handlers.authentication
http.handlers.cache
http.handlers.encode
http.handlers.error
http.handlers.file_server
http.handlers.headers
http.handlers.request_body
http.handlers.reverse_proxy
http.handlers.rewrite
http.handlers.static_response
http.handlers.subroute
http.handlers.templates
http.handlers.vars
http.matchers.file
http.matchers.header
http.matchers.header_regexp
http.matchers.host
http.matchers.method
http.matchers.not
http.matchers.path
http.matchers.path_regexp
http.matchers.protocol
http.matchers.query
http.matchers.remote_ip
http.matchers.vars
http.matchers.vars_regexp
http.reverse_proxy.circuit_breakers.local
http.reverse_proxy.selection_policies.first
http.reverse_proxy.selection_policies.header
http.reverse_proxy.selection_policies.ip_hash
http.reverse_proxy.selection_policies.least_conn
http.reverse_proxy.selection_policies.random
http.reverse_proxy.selection_policies.random_choose
http.reverse_proxy.selection_policies.round_robin
http.reverse_proxy.selection_policies.uri_hash
http.reverse_proxy.transport.fastcgi
http.reverse_proxy.transport.http
http.reverse_proxy.transport.http_ntlm
tls
tls.certificate_selection.custom
tls.certificates.automate
tls.certificates.load_files
tls.certificates.load_folders
tls.certificates.load_pem
tls.dns.cloudflare
tls.handshake_match.sni
tls.management.acme
tls.stek.distributed
tls.stek.standard