golang-sample

go-net0.go

package main

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

func main() {
	urls := []string{
		"http://example.com",
		"http://example.net",
		"http://example.co.jp",
		"http://example.org",
	}

	for _, url := range urls {
		res, err := http.Get(url)
		if err != nil {
			log.Fatal(err)
		}
		defer res.Body.Close()
		fmt.Printf("%s\t%s\n", url, res.Status)
	}

}

go-net1.go

package main

import (
	"fmt"
	"net/http"
)

func getStatus(urls []string) <-chan string {
	statusChan := make(chan string)
	for _, url := range urls {
		go func(url string) { //匿名関数
			res, err := http.Get(url)
			if err != nil {
				statusChan <- err.Error()
				return
			}
			defer res.Body.Close()
			statusChan <- fmt.Sprintf("%s\t%s", url, res.Status)
		}(url)

	}
	return statusChan
}

func main() {
	urls := []string{
		"http://example.com",
		"http://example.net",
		"http://example.co.jp",
		"http://example.org",
	}

	//内部で呼び出したゴルーチンの終了は待たずにメインスレッドは続行される
	statusChan := getStatus(urls)
	for i := 0; i < len(urls); i++ {
		fmt.Printf("%s\n", <-statusChan)
	}

}

go-net2.go

package main

import (
	"fmt"
	"net/http"
	"time"
)

func getStatus(urls []string) <-chan string {
	statusChan := make(chan string)
	for _, url := range urls {
		go func(url string) { //匿名関数
			res, err := http.Get(url)
			if err != nil {
				statusChan <- err.Error()
				return
			}
			defer res.Body.Close()
			statusChan <- fmt.Sprintf("%s\t%s", url, res.Status)
		}(url)

	}
	return statusChan
}

func getStatusWithTimeout(urls []string) {
	statusChan := getStatus(urls)
	timeout := time.After(time.Second)
	for {
		select {
		case status := <-statusChan:
			fmt.Printf("%s\n", status)
		case <-timeout:
			return
		}
	}
}

func main() {
	urls := []string{
		"http://example.com",
		"http://example.net",
		"http://example.co.jp",
		"http://example.org",
	}
	getStatusWithTimeout(urls)
}

go-net3.go

package main

import (
	"fmt"
	"net/http"
	"time"
)

func getStatus(urls []string) <-chan string {
	statusChan := make(chan string, len(urls)) //URLの数だけバッファを確保
	for _, url := range urls {
		go func(url string) { //匿名関数
			res, err := http.Get(url)
			if err != nil {
				statusChan <- err.Error()
				return
			}
			defer res.Body.Close()
			statusChan <- fmt.Sprintf("%s\t%s", url, res.Status)
		}(url)

	}
	return statusChan
}

func main() {
	urls := []string{
		"http://example.com",
		"http://example.net",
		"http://example.co.jp",
		"http://example.org",
	}

	statusChan := getStatus(urls)
	for i := 0; i < len(urls); i++ {
		fmt.Printf("%s\n", <-statusChan)
		time.Sleep(time.Second) //時間のかかる処理
	}

}

go-net4.go

package main

import (
	"fmt"
	"net/http"
)

func getStatus(urls []string) <-chan string {
	statusChan := make(chan string, len(urls)) //URLの数だけバッファを確保
	var empty struct{}
	limit := make(chan struct{}, 2) //同時ゴルーチン起動数=2
	for _, url := range urls {
		select {
		case limit <- empty:
			go func(url string) { //匿名関数
				res, err := http.Get(url)
				if err != nil {
					statusChan <- err.Error()
					return
				}
				defer res.Body.Close()
				statusChan <- fmt.Sprintf("%s\t%s", url, res.Status)
				<-limit //終わったら1つ読みだして空きを作る
			}(url)
		}

	}
	return statusChan
}

func main() {
	urls := []string{
		"http://example.com",
		"http://example.net",
		"http://example.co.jp",
		"http://example.org",
	}

	statusChan := getStatus(urls)
	for i := 0; i < len(urls); i++ {
		fmt.Printf("%s\n", <-statusChan)
	}

}

hello-io.go

package main

import (
	"bufio"
	"fmt"
	"github.com/jessevdk/go-flags"
	"os"
)

type cmdOptions struct {
	Help  bool   `short:"h" long:"help" description:"Show this help message"`
	Input string `short:"i" long:"input"`
}

func main() {
	opts := cmdOptions{}
	optparser := flags.NewParser(&opts, flags.Default)
	optparser.Name = ""
	optparser.Usage = "-i input -o output [OPTIONS]"
	optparser.Parse()

	f := os.Stdin
	if opts.Input != "" && opts.Input != "-" {
		var err error
		f, err = os.Open(opts.Input)
		if err != nil {
			fmt.Fprintf(os.Stderr, "%s\n", err)
			os.Exit(1)
		}
		defer f.Close()
	}

	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		fmt.Printf("Got [%s]\n", scanner.Text())
	}
	if err := scanner.Err(); err != nil {
		fmt.Fprintln(os.Stderr, "reading standard input:", err)
	}

}