cmd/server sets now environment variables KAPOW_DATA_URL and KAPOW_CONTROL_URL

Remove golinter error S1036: unnecessary guard around map access in 
spawn package

internal/cmd/server.go

@@ -47,6 +47,14 @@ var ServerCmd = &cobra.Command{
 		sConf.ClientAuth, _ = cmd.Flags().GetBool("clientauth")
 		sConf.ClientCaFile, _ = cmd.Flags().GetString("clientcafile")
 
+		// Set environment variables KAPOW_DATA_URL and KAPOW_CONTROL_URL only if they aren't set so we don't overwrite user's preferences
+		if _, exist := os.LookupEnv("KAPOW_DATA_URL"); !exist {
+			os.Setenv("KAPOW_DATA_URL", "http://"+sConf.DataBindAddr)
+		}
+		if _, exist := os.LookupEnv("KAPOW_CONTROL_URL"); !exist {
+			os.Setenv("KAPOW_CONTROL_URL", "http://"+sConf.DataBindAddr)
+		}
+
 		go server.StartServer(sConf)
 
 		// start sub shell + ENV(KAPOW_CONTROL_URL)
@@ -60,7 +68,7 @@ var ServerCmd = &cobra.Command{
 			kapowCMD := exec.Command("bash", powfile)
 			kapowCMD.Stdout = os.Stdout
 			kapowCMD.Stderr = os.Stderr
-			kapowCMD.Env = append(os.Environ(), "KAPOW_CONTROL_URL=http://"+sConf.ControlBindAddr)
+			kapowCMD.Env = os.Environ()
 
 			err = kapowCMD.Run()
 			if err != nil {

internal/server/data/resource.go

@@ -175,11 +175,7 @@ func setResponseHeaders(w http.ResponseWriter, r *http.Request, h *model.Handler
 	}
 
 	hds := h.Writer.Header()
-	if _, ok := hds[name]; ok {
-		hds[name] = append(hds[name], string(vb))
-	} else {
-		hds[name] = []string{string(vb)}
-	}
+	hds[name] = append(hds[name], string(vb))
 }
 
 func setResponseCookies(w http.ResponseWriter, r *http.Request, h *model.Handler) {

internal/server/user/spawn/spawn.go

@@ -44,7 +44,7 @@ func Spawn(h *model.Handler, out io.Writer) error {
 	if out != nil {
 		cmd.Stdout = out
 	}
-	cmd.Env = append(os.Environ(), "KAPOW_DATA_URL=http://localhost:8082")
+	cmd.Env = os.Environ()
 	cmd.Env = append(cmd.Env, "KAPOW_HANDLER_ID="+h.ID)
 
 	err = cmd.Run()

internal/server/user/spawn/spawn_test.go

@@ -94,6 +94,8 @@ func TestSpawnWritesToStdout(t *testing.T) {
 }
 
 func TestSpawnSetsKapowURLEnvVar(t *testing.T) {
+	t.Skip("Not neccessary as this variable is now set by server at start up")
+
 	h := &model.Handler{
 		Route: model.Route{
 			Entrypoint: locateJailLover(),