Go goroutine and channel to monitor process end

alive.go

// compile: go build -o alive
// usage:
// $ ps -A | rg firefox
// 35761 ??         0:23.28 /Applications/Firefox.app/Contents/MacOS/firefox
// ./alive 35761

package main

import (
	"fmt"
	"github.com/shirou/gopsutil/process"
	"os"
	"strconv"
	"time"
)

func die(message string) {
	fmt.Println(message)
	os.Exit(1)
}

func main() {
	if len(os.Args) != 2 {
		die("PID missing")
	}
	pid, err := strconv.Atoi(os.Args[1])
	if err != nil {
		die("Bad PID")
	}

	fmt.Printf("Monitoring %d ...\n", pid)

	// channel 'c' is used to wait for goroutine end
	c := make(chan struct{})
	go func() {
		for {
			alive, err := process.PidExists(int32(pid))
			if err != nil {
				fmt.Print("ERROR ")
			} else if err == nil && !alive {
				fmt.Printf("%d died :(\n", pid)
				// we've done
				c <- struct{}{}
			}
			time.Sleep(time.Second)
		}
	}()
	<-c
}