(goctl:) fix circle import in case new parser (#3750)

Co-authored-by: Kevin Wan <wanjunfeng@gmail.com>

tools/goctl/pkg/parser/api/importstack/importstack.go

@@ -0,0 +1,31 @@
+package importstack
+
+import "errors"
+
+// ErrImportCycleNotAllowed defines an error for circular importing
+var ErrImportCycleNotAllowed = errors.New("import cycle not allowed")
+
+// ImportStack a stack of import paths
+type ImportStack []string
+
+func New() *ImportStack {
+	return &ImportStack{}
+}
+
+func (s *ImportStack) Push(p string) error {
+	for _, x := range *s {
+		if x == p {
+			return ErrImportCycleNotAllowed
+		}
+	}
+	*s = append(*s, p)
+	return nil
+}
+
+func (s *ImportStack) Pop() {
+	*s = (*s)[0 : len(*s)-1]
+}
+
+func (s *ImportStack) List() []string {
+	return *s
+}