Add basic federation example (#26)

Add basic federation example

examples/basic-federation/client/main.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"time"
+
+	"github.com/smallstep/certificates/ca"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Fprintf(os.Stderr, "Usage: %s <token>\n", os.Args[0])
+		os.Exit(1)
+	}
+
+	token := os.Args[1]
+
+	// make sure to cancel the renew goroutine
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	client, err := ca.BootstrapClient(ctx, token, ca.AddFederationToRootCAs())
+	if err != nil {
+		panic(err)
+	}
+
+	for {
+		resp, err := client.Get("https://127.0.0.1:8443")
+		if err != nil {
+			panic(err)
+		}
+		b, err := ioutil.ReadAll(resp.Body)
+		resp.Body.Close()
+		if err != nil {
+			panic(err)
+		}
+
+		fmt.Printf("Server responded: %s\n", b)
+		time.Sleep(5 * time.Second)
+	}
+}