實作ping flag

package main

import (
	"flag"
	"fmt"
	"log"
	"net/http"
	"os"
)

func handler(w http.ResponseWriter, r *http.Request) {
	log.Println("http request!!!!")
	fmt.Fprintf(w, "I love %s!", r.URL.Path[1:])
}
func pinger(port string) error {
	resp, err := http.Get("http://172.20.10.10:" + port)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode != 200 {
		return fmt.Errorf("server returned not 200 status code")
	}
	return nil
}
func main() {
	var port string
	var ping bool
	flag.StringVar(&port, "port", "3001", "server port")
	flag.StringVar(&port, "p", "3001", "server port")
	flag.BoolVar(&ping, "ping", false, "check server live")
	flag.Parse()
	if p, ok := os.LookupEnv("PORT"); ok {
		port = p
	}
	if ping {
		if err := pinger(port); err != nil {
			log.Printf("ping server error: %v\n ", err)
		}
		return // 就不會執行下面的http handler
	}
	http.HandleFunc("/", handler)
	log.Println("http server run on " + port + " port")
	log.Fatal(http.ListenAndServe(":"+port, nil))
}

開啟另外一個terminal 並下command run起3001 port

go run main.go -p 3001

另一個terminal 就針對3001 port ping

go run main.go -p 3001 -ping

可以看到第一個terminal有被執行到handler．裡頭有個log被觸發

剩餘的 明日再研究