Add unit test for proxy and shutdown channel

* Proxy has initial unit test and more can be added
* Shutdown channel and cancellation added for proper shutdown of
the proxy

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

pkg/proxy_test.go

@@ -0,0 +1,73 @@
+package pkg
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"sync"
+	"testing"
+	"time"
+)
+
+func Test_Proxy_ToPrivateServer(t *testing.T) {
+
+	wantBodyText := "OK"
+	wantBody := []byte(wantBodyText)
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+
+		if r.Body != nil {
+			defer r.Body.Close()
+		}
+
+		w.WriteHeader(http.StatusOK)
+		w.Write(wantBody)
+
+	}))
+
+	defer upstream.Close()
+	port := 8080
+	proxy := NewProxy(port, time.Second*1)
+
+	gwChan := make(chan string, 1)
+	doneCh := make(chan bool)
+
+	go proxy.Start(gwChan, doneCh)
+
+	u, _ := url.Parse(upstream.URL)
+	log.Println("Host", u.Host)
+	wg := sync.WaitGroup{}
+	wg.Add(1)
+	go func() {
+		gwChan <- u.Host
+		wg.Done()
+	}()
+	wg.Wait()
+
+	req, err := http.NewRequest(http.MethodGet, fmt.Sprintf("http://127.0.0.1:%d", port), nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for i := 1; i < 11; i++ {
+		res, err := http.DefaultClient.Do(req)
+		if err != nil {
+			t.Logf("Try %d, gave error: %s", i, err)
+
+			time.Sleep(time.Millisecond * 100)
+		} else {
+
+			resBody, _ := ioutil.ReadAll(res.Body)
+			if string(resBody) != string(wantBody) {
+				t.Errorf("want %s, but got %s in body", string(wantBody), string(resBody))
+			}
+			break
+		}
+	}
+
+	go func() {
+		doneCh <- true
+	}()
+}