Remove global cfg variable (fixes #2294)

Not necessarily the easiest way to fix just this bug, but the root cause
was using the (at that point uninitialized) cfg variable, so it seemed
sensible to just get rid of it to avoid that kind of crap.

cmd/syncthing/usage_report.go

@@ -32,12 +32,14 @@ import (
 const usageReportVersion = 2
 
 type usageReportingManager struct {
+	cfg   *config.Wrapper
 	model *model.Model
 	sup   *suture.Supervisor
 }
 
-func newUsageReportingManager(m *model.Model, cfg *config.Wrapper) *usageReportingManager {
+func newUsageReportingManager(cfg *config.Wrapper, m *model.Model) *usageReportingManager {
 	mgr := &usageReportingManager{
+		cfg:   cfg,
 		model: m,
 	}
 
@@ -58,9 +60,7 @@ func (m *usageReportingManager) VerifyConfiguration(from, to config.Configuratio
 func (m *usageReportingManager) CommitConfiguration(from, to config.Configuration) bool {
 	if to.Options.URAccepted >= usageReportVersion && m.sup == nil {
 		// Usage reporting was turned on; lets start it.
-		svc := &usageReportingService{
-			model: m.model,
-		}
+		svc := newUsageReportingService(m.cfg, m.model)
 		m.sup = suture.NewSimple("usageReporting")
 		m.sup.Add(svc)
 		m.sup.ServeBackground()
@@ -79,7 +79,7 @@ func (m *usageReportingManager) String() string {
 
 // reportData returns the data to be sent in a usage report. It's used in
 // various places, so not part of the usageReportingSvc object.
-func reportData(m *model.Model) map[string]interface{} {
+func reportData(cfg *config.Wrapper, m *model.Model) map[string]interface{} {
 	res := make(map[string]interface{})
 	res["urVersion"] = usageReportVersion
 	res["uniqueID"] = cfg.Options().URUniqueID
@@ -238,12 +238,21 @@ func stringIn(needle string, haystack []string) bool {
 }
 
 type usageReportingService struct {
+	cfg   *config.Wrapper
 	model *model.Model
 	stop  chan struct{}
 }
 
+func newUsageReportingService(cfg *config.Wrapper, model *model.Model) *usageReportingService {
+	return &usageReportingService{
+		cfg:   cfg,
+		model: model,
+		stop:  make(chan struct{}),
+	}
+}
+
 func (s *usageReportingService) sendUsageReport() error {
-	d := reportData(s.model)
+	d := reportData(s.cfg, s.model)
 	var b bytes.Buffer
 	json.NewEncoder(&b).Encode(d)
 
@@ -256,12 +265,12 @@ func (s *usageReportingService) sendUsageReport() error {
 		}
 	}
 
-	if cfg.Options().URPostInsecurely {
+	if s.cfg.Options().URPostInsecurely {
 		transp.TLSClientConfig = &tls.Config{
 			InsecureSkipVerify: true,
 		}
 	}
-	_, err := client.Post(cfg.Options().URURL, "application/json", &b)
+	_, err := client.Post(s.cfg.Options().URURL, "application/json", &b)
 	return err
 }
 
@@ -271,7 +280,7 @@ func (s *usageReportingService) Serve() {
 	l.Infoln("Starting usage reporting")
 	defer l.Infoln("Stopping usage reporting")
 
-	t := time.NewTimer(time.Duration(cfg.Options().URInitialDelayS) * time.Second) // time to initial report at start
+	t := time.NewTimer(time.Duration(s.cfg.Options().URInitialDelayS) * time.Second) // time to initial report at start
 	for {
 		select {
 		case <-s.stop: