make the simple and allocator examples runnable

This way, not only do we ensure that they always build, they're also
verified as part of 'go test'.

_example/allocactor.go

@@ -1,26 +0,0 @@
-package main
-
-import (
-	"context"
-	"log"
-
-	"github.com/chromedp/chromedp"
-)
-
-func main() {
-	dockerAllocatorOpts := []chromedp.DockerAllocatorOption{}
-
-	ctxt, cancel := chromedp.NewAllocator(context.Background(), chromedp.WithDockerAllocator(dockerAllocatorOpts...))
-	defer cancel()
-
-	task1Context, cancel := chromedp.NewContext(ctxt)
-	defer cancel()
-
-	if err := chromedp.Run(task1Context, myTask()); err != nil {
-		log.Fatal(err)
-	}
-}
-
-func myTask() chromedp.Tasks {
-	return []chromedp.Action{}
-}

_example/simple.go

@@ -1,36 +0,0 @@
-package main
-
-import (
-	"context"
-	"fmt"
-	"log"
-
-	"github.com/chromedp/chromedp"
-)
-
-func main() {
-	// create a new context
-	ctx, cancel := chromedp.NewContext(context.Background())
-	defer cancel()
-
-	// grab the title
-	var title string
-	if err := chromedp.Run(ctx, grabTitle(&title)); err != nil {
-		log.Fatal(err)
-	}
-
-	// print it
-	fmt.Println(title)
-
-	// ensure all resources are cleaned up
-	cancel()
-	chromedp.FromContext(ctx).Wait()
-}
-
-func grabTitle(title *string) chromedp.Tasks {
-	return []chromedp.Action{
-		chromedp.Navigate("https://github.com/"),
-		chromedp.WaitVisible("#start-of-content", chromedp.ByID),
-		chromedp.Title(title),
-	}
-}

example_test.go

@@ -0,0 +1,79 @@
+package chromedp_test
+
+import (
+	"context"
+	"fmt"
+	"io/ioutil"
+	"os"
+
+	"github.com/chromedp/chromedp"
+)
+
+func ExampleTitle() {
+	ctx, cancel := chromedp.NewContext(context.Background())
+	defer cancel()
+
+	var title string
+	if err := chromedp.Run(ctx, chromedp.Tasks{
+		chromedp.Navigate("https://github.com/chromedp/chromedp/issues"),
+		chromedp.WaitVisible("#start-of-content", chromedp.ByID),
+		chromedp.Title(&title),
+	}); err != nil {
+		panic(err)
+	}
+
+	fmt.Println(title)
+
+	// wait for the resources to be cleaned up
+	cancel()
+	chromedp.FromContext(ctx).Wait()
+
+	// Output:
+	// Issues · chromedp/chromedp · GitHub
+}
+
+func ExampleExecAllocatorOption() {
+	dir, err := ioutil.TempDir("", "chromedp-example")
+	if err != nil {
+		panic(err)
+	}
+	defer os.RemoveAll(dir)
+
+	opts := []chromedp.ExecAllocatorOption{
+		chromedp.NoFirstRun,
+		chromedp.NoDefaultBrowserCheck,
+		chromedp.Headless,
+		chromedp.DisableGPU,
+		chromedp.UserDataDir(dir),
+	}
+
+	allocCtx, cancel := chromedp.NewAllocator(context.Background(),
+		chromedp.WithExecAllocator(opts...))
+	defer cancel()
+
+	taskCtx, cancel := chromedp.NewContext(allocCtx)
+	defer cancel()
+
+	// ensure that the browser process is started
+	if err := chromedp.Run(taskCtx, chromedp.Tasks{}); err != nil {
+		panic(err)
+	}
+
+	files, err := ioutil.ReadDir(dir)
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println("Files in UserDataDir:")
+	for _, file := range files {
+		fmt.Println(file.Name())
+	}
+
+	// wait for the resources to be cleaned up
+	cancel()
+	chromedp.FromContext(allocCtx).Wait()
+
+	// Output:
+	// Files in UserDataDir:
+	// Default
+	// DevToolsActivePort
+}