tests: Run select statement in separate goroutine (#4499)

Instead of after the wg.Wait() so as to make sure that the 'earliest'
of the two select case that becomes active is selected..

cmd/server-mux_test.go

@@ -309,34 +309,36 @@ func TestServerListenAndServePlain(t *testing.T) {
 	// ListenAndServe in a goroutine, but we don't know when it's ready
 	go func() { errc <- m.ListenAndServe("", "") }()
 
-	wg := &sync.WaitGroup{}
-	wg.Add(1)
 	// Keep trying the server until it's accepting connections
 	go func() {
 		client := http.Client{Timeout: time.Millisecond * 10}
-		ok := false
-		for !ok {
+		for {
 			res, _ := client.Get("http://" + addr)
 			if res != nil && res.StatusCode == http.StatusOK {
-				ok = true
+				break
 			}
 		}
+	}()
 
-		wg.Done()
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		select {
+		case err := <-errc:
+			if err != nil {
+				t.Fatal(err)
+			}
+		case <-wait:
+			return
+		}
 	}()
 
+	// Wait until we get an error or wait closed
 	wg.Wait()
 
-	// Block until we get an error or wait closed
-	select {
-	case err := <-errc:
-		if err != nil {
-			t.Fatal(err)
-		}
-	case <-wait:
-		m.Close() // Shutdown the ServerMux
-		return
-	}
+	// Shutdown the ServerMux
+	m.Close()
 }
 
 func TestServerListenAndServeTLS(t *testing.T) {
@@ -389,12 +391,11 @@ func TestServerListenAndServeTLS(t *testing.T) {
 			Timeout:   time.Millisecond * 10,
 			Transport: tr,
 		}
-		okTLS := false
 		// Keep trying the server until it's accepting connections
-		for !okTLS {
+		for {
 			res, _ := client.Get("https://" + addr)
 			if res != nil && res.StatusCode == http.StatusOK {
-				okTLS = true
+				break
 			}
 		}
 
@@ -423,19 +424,25 @@ func TestServerListenAndServeTLS(t *testing.T) {
 		wg.Done()
 	}()
 
-	wg.Wait()
-
-	// Block until we get an error or wait closed
-	select {
-	case err := <-errc:
-		if err != nil {
-			t.Error(err)
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		select {
+		case err := <-errc:
+			if err != nil {
+				t.Error(err)
+				return
+			}
+		case <-wait:
 			return
 		}
-	case <-wait:
-		m.Close() // Shutdown the ServerMux
-		return
-	}
+	}()
+
+	// Wait until we get an error or wait closed
+	wg.Wait()
+
+	// Shutdown the ServerMux
+	m.Close()
 }
 
 // generateTestCert creates a cert and a key used for testing only