build, cmd, lib: Minimum supported compiler version is Go 1.5

cmd/stfinddevice/main.go

@@ -66,7 +66,7 @@ func checkServers(deviceID protocol.DeviceID, servers ...string) {
 		}()
 	}
 
-	for _ = range servers {
+	for range servers {
 		res := <-resc
 
 		u, _ := url.Parse(res.server)

cmd/strelaysrv/main.go

@@ -212,7 +212,7 @@ func main() {
 
 func monitorLimits() {
 	limitCheckTimer = time.NewTimer(time.Minute)
-	for _ = range limitCheckTimer.C {
+	for range limitCheckTimer.C {
 		if atomic.LoadInt64(&numConnections)+atomic.LoadInt64(&numProxies) > descriptorLimit {
 			atomic.StoreInt32(&overLimit, 1)
 			log.Println("Gone past our connection limits. Starting to refuse new/drop idle connections.")

cmd/stvanity/main.go

@@ -130,7 +130,7 @@ func printProgress(prefix string, count *int64) {
 	expectedIterations := float64(int(1) << uint(wantBits))
 	fmt.Printf("Want %d bits for prefix %q, about %.2g certs to test (statistically speaking)\n", wantBits, prefix, expectedIterations)
 
-	for _ = range time.NewTicker(15 * time.Second).C {
+	for range time.NewTicker(15 * time.Second).C {
 		tried := atomic.LoadInt64(count)
 		elapsed := time.Since(started)
 		rate := float64(tried) / elapsed.Seconds()

cmd/syncthing/gui_solaris.go

@@ -78,7 +78,7 @@ func trackCPUUsage() {
 	var prevTime = time.Now().UnixNano()
 	var rusage prusage_t
 	var pid = os.Getpid()
-	for _ = range time.NewTicker(time.Second).C {
+	for range time.NewTicker(time.Second).C {
 		err := solarisPrusage(pid, &rusage)
 		if err != nil {
 			l.Warnln("getting prusage:", err)

cmd/syncthing/gui_unix.go

@@ -21,7 +21,7 @@ func trackCPUUsage() {
 	var prevUsage int64
 	var prevTime = time.Now().UnixNano()
 	var rusage syscall.Rusage
-	for _ = range time.NewTicker(time.Second).C {
+	for range time.NewTicker(time.Second).C {
 		syscall.Getrusage(syscall.RUSAGE_SELF, &rusage)
 		curTime := time.Now().UnixNano()
 		timeDiff := curTime - prevTime

cmd/syncthing/gui_windows.go

@@ -34,7 +34,7 @@ func trackCPUUsage() {
 	prevTime := ctime.Nanoseconds()
 	prevUsage := ktime.Nanoseconds() + utime.Nanoseconds() // Always overflows
 
-	for _ = range time.NewTicker(time.Second).C {
+	for range time.NewTicker(time.Second).C {
 		err := syscall.GetProcessTimes(handle, &ctime, &etime, &ktime, &utime)
 		if err != nil {
 			continue