wip: pipe stdout & stderr

cmd/experiment/.gitignore

@@ -0,0 +1,2 @@
+/dummy/dummy
+/starter/starter

cmd/experiment/dummy/dummy.go

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"time"
+)
+
+func main() {
+	for i := 0; i < 10; i++ {
+		log.Println("using log.Println")
+		fmt.Println("using fmt.Println")
+		time.Sleep(time.Millisecond * 500)
+	}
+
+	log.Println("log: finishing up")
+	fmt.Println("fmt: finishing up")
+}

cmd/experiment/starter/starter.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"bufio"
+	"io"
+	"log"
+	"os/exec"
+	"sync"
+)
+
+const (
+	DummyPath = "/workspaces/wingmate/cmd/experiment/dummy/dummy"
+)
+
+func main() {
+	var (
+		stdout io.ReadCloser
+		stderr io.ReadCloser
+		wg     *sync.WaitGroup
+		err    error
+	)
+	cmd := exec.Command(DummyPath)
+
+	if stdout, err = cmd.StdoutPipe(); err != nil {
+		log.Panic(err)
+	}
+
+	if stderr, err = cmd.StderrPipe(); err != nil {
+		log.Panic(err)
+	}
+
+	wg = &sync.WaitGroup{}
+	wg.Add(2)
+	go pulley(wg, stdout, "stdout")
+	go pulley(wg, stderr, "stderr")
+
+	if err = cmd.Start(); err != nil {
+		log.Panic(err)
+	}
+	wg.Wait()
+
+	if err = cmd.Wait(); err != nil {
+		log.Printf("got error when Waiting for child process: %#v\n", err)
+	}
+}
+
+func pulley(wg *sync.WaitGroup, src io.ReadCloser, srcName string) {
+	defer wg.Done()
+
+	scanner := bufio.NewScanner(src)
+	for scanner.Scan() {
+		log.Printf("coming out from %s: %s\n", srcName, scanner.Text())
+	}
+
+	if err := scanner.Err(); err != nil {
+		log.Printf("got error whean reading from %s: %#v\n", srcName, err)
+	}
+
+	log.Printf("closing %s...\n", srcName)
+	_ = src.Close()
+}