增加scanf时的默认值

fast_trace/fast_trace ipv6.go

@@ -107,7 +107,7 @@ func FastTestv6(tm bool, outEnable bool) {
 	fmt.Print("请选择选项：")
 	_, err := fmt.Scanln(&c)
 	if err != nil {
-		return
+		c = "1"
 	}
 
 	ft := FastTracer{}

fast_trace/fast_trace.go

@@ -121,7 +121,7 @@ func FastTest(tm bool, outEnable bool) {
 	fmt.Print("请选择选项：")
 	_, err := fmt.Scanln(&c)
 	if err != nil {
-		return
+		c = "1"
 	}
 	if c == "2" {
 		FastTestv6(tm, outEnable)
@@ -132,7 +132,7 @@ func FastTest(tm bool, outEnable bool) {
 	fmt.Print("请选择选项：")
 	_, err = fmt.Scanln(&c)
 	if err != nil {
-		return
+		c = "1"
 	}
 
 	ft := FastTracer{}

util/util.go

@@ -110,7 +110,7 @@ func DomainLookUp(host string, ipv4Only bool, dotServer string) net.IP {
 		fmt.Printf("Your Option: ")
 		_, err := fmt.Scanln(&index)
 		if err != nil {
-			return nil
+			index = 0
 		}
 		if index >= len(ips) || index < 0 {
 			fmt.Println("Your Option is invalid")