Fixed RmFront panic.

api/modem/at/response.go

@@ -9,12 +9,13 @@ func (resp Resp) Check() bool {
 }
 
 func (resp Resp) RmFront(str string) Resp {
-	if !resp.Check() {
-		return RespNil
-	}
 	return Resp(string(resp)[len(str):])
 }
 
+func (resp Resp) CheckFront(str string) bool {
+	return len(resp) >= len(str) && resp[:len(str)].String() == str
+}
+
 func (resp Resp) String() string {
 	return string(resp)
 }

api/modem/gps/gps.go

@@ -49,9 +49,10 @@ func (g *gps) Update() error {
 	if err != nil {
 		return fmt.Errorf("receive GPS data: %w", err)
 	}
-	if !resp.Check() {
+	if !resp.Check() || !resp.CheckFront("+CGPSINFO:") {
 		return fmt.Errorf("get GPS info: error response: %s", resp)
 	}
+
 	if err := g.data.decode(strings.Split(strings.Replace(resp.RmFront("+CGPSINFO:").String(), "\r", "", -1), "\n")[0]); err != nil {
 		g.logger.Printf("error decode: %s\n", err.Error())
 	}
@@ -86,7 +87,7 @@ func (g *gps) switchGpsMode(on bool) error {
 	if err != nil {
 		return fmt.Errorf("make at ask: %w", err)
 	}
-	if !resp.Check() {
+	if !resp.Check() || !resp.CheckFront("+CGPS:") {
 		return fmt.Errorf("get GPS mode: error response: %s", resp)
 	}
 	ans := strings.Replace(strings.Split(strings.Split(resp.RmFront("+CGPS:").String(), "\n")[0], ",")[0], " ", "", -1)

main.go

@@ -18,6 +18,7 @@ func main() {
 func mainE() error {
 	logger := log.New(os.Stdout, "main : ", log.LstdFlags)
 	m := modem.New(log.New(logger.Writer(), "modem : ", log.LstdFlags))
+
 	logger.Println("||||||||||||||||| INIT |||||||||||||||")
 	if err := m.Init(); err != nil {
 		logger.Println("Init ended with error:", err.Error())
@@ -34,6 +35,10 @@ func mainE() error {
 		logger.Println("AAAAAAAAAAAAAAA Modem is not connected")
 		return nil
 	}
+	// m.PowerOff()
+	// time.Sleep(10 * time.Second)
+	// m.PowerOn()
+
 	logger.Println("||||||||||||||||| GET INFO |||||||||||||||||")
 	logger.Println(m.Update())
 	logger.Printf("DATA: %+v\n", m.GetData())