add goreleaser configurations

.github/workflows/release.yml

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+name: goreleaser
+
+on:
+  push:
+    # run only against tags
+    tags:
+      - '*'
+
+permissions:
+  contents: write
+
+jobs:
+  goreleaser:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+      - run: git fetch --force --tags
+      - uses: actions/setup-go@v3
+        with:
+          go-version: '>=1.19.2'
+          cache: true
+      - uses: goreleaser/goreleaser-action@v2
+        with:
+          distribution: goreleaser
+          version: latest
+          args: release --rm-dist
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.gitignore

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+.idea
+dist/
+.telmon-config.yaml

.goreleaser.yaml

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+before:
+  hooks:
+    # You may remove this if you don't use go modules.
+    - go mod tidy
+
+builds:
+  - env:
+      - CGO_ENABLED=0
+    goos:
+      - linux
+      - windows
+      - darwin
+    goarch:
+      - amd64
+      - arm64
+    flags:
+      - -mod=vendor
+
+archives:
+  - replacements:
+      darwin: Darwin
+      linux: Linux
+      windows: Windows
+      386: i386
+      amd64: x86_64
+
+checksum:
+  name_template: 'checksums.txt'
+
+release:
+  prerelease: auto
+
+universal_binaries:
+  - replace: true
+
+snapshot:
+  name_template: "{{ incpatch .Version }}-next"
+
+changelog:
+  sort: asc
+  filters:
+    exclude:
+      - '^docs:'
+      - '^test:'
+

go.mod

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+module github.com/jackkweyunga/telmon
+
+go 1.19
+
+require (
+	github.com/mitchellh/mapstructure v1.5.0
+	github.com/reiver/go-telnet v0.0.0-20180421082511-9ff0b2ab096e
+	gopkg.in/yaml.v3 v3.0.1
+)
+
+require (
+	github.com/fsnotify/fsnotify v1.5.4 // indirect
+	github.com/hashicorp/hcl v1.0.0 // indirect
+	github.com/kr/pretty v0.3.0 // indirect
+	github.com/magiconair/properties v1.8.6 // indirect
+	github.com/pelletier/go-toml v1.9.5 // indirect
+	github.com/pelletier/go-toml/v2 v2.0.5 // indirect
+	github.com/reiver/go-oi v1.0.0 // indirect
+	github.com/spf13/afero v1.8.2 // indirect
+	github.com/spf13/cast v1.5.0 // indirect
+	github.com/spf13/jwalterweatherman v1.1.0 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
+	github.com/spf13/viper v1.13.0 // indirect
+	github.com/subosito/gotenv v1.4.1 // indirect
+	golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a // indirect
+	golang.org/x/text v0.3.7 // indirect
+	gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 // indirect
+	gopkg.in/ini.v1 v1.67.0 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
+)

main.go

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+package main
+
+import (
+	"fmt"
+	"github.com/spf13/viper"
+	"log"
+	"os"
+	"os/signal"
+	"time"
+)
+
+type Config struct {
+	Port      int      `mapstructure:"port"`
+	Addr      string   `mapstructure:"addr"`
+	Password  string   `mapstructure:"password"`
+	Email     string   `mapstructure:"email"`
+	Receivers []string `mapstructure:"receivers"`
+}
+
+func main() {
+
+	config, err := LoadConfig()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println(config)
+
+	var (
+		port      = config.Port
+		addr      = config.Addr
+		fromEmail = config.Email
+		password  = config.Password
+		receivers = config.Receivers
+	)
+
+	c := make(chan os.Signal, 1)
+
+	// Notify on any interrupt
+	signal.Notify(c, os.Interrupt)
+
+	isShuttingDown := false
+	started := false
+
+OUTER:
+	for {
+		if isShuttingDown {
+			break
+		}
+
+		select {
+		case s, ok := <-c:
+			if ok {
+				fmt.Println("Service is going down.")
+				fmt.Printf("Received signal %v \n", s)
+				isShuttingDown = true
+				c = nil
+				continue OUTER
+			}
+		default:
+			if !started {
+				println("Monitoring Service started successfully ...")
+				started = true
+			}
+
+			t := time.Now()
+			fmt.Printf("[%s] running \n", t.Format(time.RFC3339))
+			Monitor(addr, port, fromEmail, password, receivers)
+			time.Sleep(10000 * time.Millisecond)
+
+		}
+	}
+}
+
+var vp *viper.Viper
+
+func LoadConfig() (Config, error) {
+	vp = viper.New()
+	var config Config
+
+	vp.SetConfigName(".telmon-config")
+	vp.SetConfigType("yaml")
+	vp.AddConfigPath(".")
+	err := vp.ReadInConfig()
+	if err != nil {
+		return Config{}, err
+	}
+
+	err = vp.Unmarshal(&config)
+	if err != nil {
+		return Config{}, err
+	}
+
+	return config, nil
+}

readme.md

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+<samp>
+
+# telmon
+
+## What is it?
+
+Telmon is a simple golang daemon that will monitor a given telnet connection from a telnet client to a telnet server. 
+It reports any loss in connection via `email` to a list of receivers.
+
+## How to use it.
+
+### 1. Installation.
+Install telmon binary from GitHub.
+
+```shell
+wget <github-path>.tar.gz
+```
+
+Extract to `/usr/local/bin/`
+
+```shell
+tar -O /usr/local/bin -xzf <github-path>.tar.gz
+```
+
+- visit the packages page for system specific binaries.
+
+In order to use telmon, create a configuration file ``.telmon-config.yaml`` in any directory in which you will run the 
+telmon binary.
+
+### 2. Configurations
+
+```shell
+$ mkdir telmon
+$ cd telmon
+$ nano .telmon-config.yaml
+```
+
+The content of the configuration file should be as follows.
+```yaml
+---
+addr: example.com
+port: <telnet-port>
+email: <sender-email>
+password: <sender-email-password>
+receivers:
+  - user-1@example.com
+  - user-2@example.com
+```
+
+### 3. Run
+
+```shell
+$ telmon
+```
+
+### 4. Supervisord
+
+Supervisord helps to monitor and control running processes
+in any linux machine. For linux users, add a supervisord configuration
+file to monitor telmon.
+
+> create a file /etc/supervisord/conf.d/telmon.conf
+
+Add the content below.
+
+```editorconfig
+[program:telmon]
+directory=/path/to/your/telmon/directory
+command=telmon
+autostart=true
+autorestart=true
+stderr_logfile=/var/log/telmon.err.log
+stdout_logfile=/var/log/telmon.out.log
+```
+
+Reload supervisord configurations.
+```shell
+supervisorctl reread
+supervisorctl update
+```
+
+OR .. reload supervisor
+```shell
+supervisorctl reload
+```
+
+## Credits
+
+- The [viper project](https://github.com/spf13/viper)
+- The [go-telnet project](https://github.com/reiver/go-telnet)
+
+</samp>

report.go

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+package main
+
+import (
+	"fmt"
+	"net/smtp"
+	"os"
+)
+
+func sendMail(msg string, from string, password string, toList []string) {
+
+	host := "smtp.gmail.com"
+	port := "587"
+
+	// We can't send strings directly in mail,
+	// strings need to be converted into slice bytes
+	body := []byte(msg)
+
+	// PlainAuth uses the given username and password to
+	// authenticate to host and act as identity.
+	// Usually identity should be the empty string,
+	// to act as username.
+	auth := smtp.PlainAuth("", from, password, host)
+
+	// SendMail uses TLS connection to send the mail
+	// The email is sent to all address in the toList,
+	// the body should be of type bytes, not strings
+	// This returns error if any occurred.
+	err := smtp.SendMail(host+":"+port, auth, from, toList, body)
+
+	// handling the errors
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+}

server/telnet-server.go

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+package main
+
+import (
+	"fmt"
+	"github.com/reiver/go-telnet"
+	"net"
+)
+
+func main() {
+	RunTelnetServer()
+}
+
+var (
+	Port = 5555
+	//Listener net.Listener
+)
+
+type Server telnet.Server
+
+func handler(port int) telnet.Handler {
+	return telnet.EchoHandler
+}
+
+func RunTelnetServer() error {
+	server := &Server{Addr: fmt.Sprintf(":%v", Port), Handler: handler(Port)}
+	err := server.MyListenAndServe()
+
+	if nil != err {
+		//@TODO: Handle this error better.
+		panic(err)
+	}
+	return err
+}
+
+func StopTelnetServer(listener net.Listener) {
+	fmt.Println("[Telnet] Shutting down ...")
+	listener.Close()
+}
+
+func (server *Server) MyListenAndServe() error {
+
+	addr := server.Addr
+	if "" == addr {
+		addr = ":telnet"
+	}
+
+	listener, err := net.Listen("tcp", addr)
+	if nil != err {
+		return err
+	}
+
+	//Listener = listener
+	fmt.Println("[Telnet] Listening at port: ", Port)
+	return telnet.Serve(listener, handler(Port))
+}