Add Cloudflare DNS record update support

.gitignore

@@ -13,3 +13,6 @@
 
 # Dependency directories (remove the comment below to include it)
 # vendor/
+
+.idea
+bin/

LICENSE

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+MIT License
+
+Copyright (c) 2018 Praveen Premaratne
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

Makefile

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+BINARY = DynDNS
+GOARCH = amd64
+
+VERSION?=latest
+
+# Symlink into GOPATH
+GITHUB_USERNAME=praveenprem
+BUILD_DIR=${GOPATH}/src/github.com/${GITHUB_USERNAME}/${BINARY}
+BIN_DIR=${BUILD_DIR}/bin
+CURRENT_DIR=\$(shell pwd)
+BUILD_DIR_LINK=\$(shell readlink ${BUILD_DIR})
+
+# Setup the -ldflags option for go build here, interpolate the variable values
+LDFLAGS = -ldflags "-X main.VERSION=${VERSION}"
+
+export GO111MODULE=on
+export GOPROXY=direct
+export GOSUMDB=off
+
+help:
+	@echo "Usage: make [command] [option]"
+	@echo "\nCommands:"
+	@echo "\t run \t\t-- Run dev environment on machine"
+	@echo "\t linux \t\t-- Build application for Linux operating systems"
+	@echo "\t build \t\t-- Build the application for Darwin"
+	@echo "\t package \t-- Tar installation archive of binary and resources"
+	@echo "\t release \t-- Release new version of the application (build, package and clean)"
+	@echo "\t install \t-- Install the binary to system"
+	@echo "\t upgrade \t-- Upgrade Go Mod versions"
+	@echo "\t dep \t\t-- Resolve mods in the go.mod file"
+	@echo "\t clean \t\t-- Clean build artefacts post package"
+	@echo "\nOptions:"
+	@echo "\t BINARY \t-- Name of the application"
+	@echo "\t GOARCH \t-- Architecture of the application"
+	@echo "\t VERSION \t-- Application version"
+
+run:
+	@go run .
+
+linux:
+	GOOS=linux GOARCH=${GOARCH} go build ${LDFLAGS} -o ${BIN_DIR}/${BINARY}-linux-${GOARCH}/${VERSION}/${BINARY}/${BINARY} .
+
+build:
+	GOOS=darwin GOARCH=${GOARCH} go build ${LDFLAGS} -o ${BIN_DIR}/${BINARY} .
+
+package:
+	@cp -r resources/ ${BIN_DIR}/${BINARY}-linux-${GOARCH}/${VERSION}/${BINARY}/
+	@mkdir -p ${BIN_DIR}/${VERSION}/
+	@tar -cvjf ${BIN_DIR}/${VERSION}/${BINARY}-linux-${GOARCH}.tar -C ${BIN_DIR}/${BINARY}-linux-${GOARCH}/${VERSION}/ .
+
+release: linux package clean
+
+install:
+	install ${BIN_DIR}/${BINARY} /usr/local/bin/${BINARY}
+
+upgrade:
+	@go get -u ./...
+
+dep:
+	@go list -m -u all
+
+clean:
+	@rm -rf ${BIN_DIR}/${BINARY}-*-${GOARCH}
+	@rm -rf ${BIN_DIR}/${BINARY}

README.md

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+# DynDNS - Dynamic DNS
+
+DynDNS is a tool to update public IP address of the network the tool is running on. 
+This relies on [ipify.org](https://www.ipify.org/)'s API to get the public IP of your network.
+
+## Currently, supported DNS providers:
+- Cloudflare
+
+## Environment variables
+- `CF_token`: Cloudflare API Token
+- `Domain`: Domain name to use
+- `Hostname`: Subdomain of the Domain above to set the record
+- `CF_proxy_disabled`: If set this will disable the proxy feature of the Cloudflare. **Enabled by default**
+
+```bash
+export CF_token=''
+export Domain=''
+export Subdomain=''
+```
+### Cloudflare API token
+Follow the [Managing API Tokens and Keys](https://support.cloudflare.com/hc/en-us/articles/200167836-Managing-API-Tokens-and-Keys) documentation to create an API token for Cloudflare