Optimize model naming (#910)

* add unit test

* fix #907

* format code

* format code

* format code

Co-authored-by: anqiansong <anqiansong@xiaoheiban.cn>

tools/goctl/util/string.go

@@ -32,3 +32,35 @@ func Index(slice []string, item string) int {
 
 	return -1
 }
+
+// SafeString converts the input string into a safe naming style in golang
+func SafeString(in string) string {
+	if len(in) == 0 {
+		return in
+	}
+
+	data := strings.Map(func(r rune) rune {
+		if isSafeRune(r) {
+			return r
+		}
+		return '_'
+	}, in)
+
+	headRune := rune(data[0])
+	if isNumber(headRune) {
+		return "_" + data
+	}
+	return data
+}
+
+func isSafeRune(r rune) bool {
+	return isLetter(r) || isNumber(r) || r == '_'
+}
+
+func isLetter(r rune) bool {
+	return 'A' <= r && r <= 'z'
+}
+
+func isNumber(r rune) bool {
+	return '0' <= r && r <= '9'
+}