(goctl): fix nested struct generation (#4281)

tools/goctl/api/spec/name.go

@@ -30,9 +30,19 @@ func (t DefineStruct) Documents() []string {
 	return t.Docs
 }
 
-// IsNestedStruct returns whether the structure is nested.
-func (t DefineStruct) IsNestedStruct() bool {
-	return len(t.Members) > 0
+// Name returns a structure string, such as User
+func (t NestedStruct) Name() string {
+	return t.RawName
+}
+
+// Comments returns the comments of struct
+func (t NestedStruct) Comments() []string {
+	return nil
+}
+
+// Documents returns the documents of struct
+func (t NestedStruct) Documents() []string {
+	return t.Docs
 }
 
 // Name returns a map string, such as map[string]int

tools/goctl/api/spec/spec.go

@@ -105,6 +105,13 @@ type (
 		Docs    Doc
 	}
 
+	// NestedStruct describes a structure nested in structure.
+	NestedStruct struct {
+		RawName string
+		Members []Member
+		Docs    Doc
+	}
+
 	// PrimitiveType describes the basic golang type, such as bool,int32,int64, ...
 	PrimitiveType struct {
 		RawName string