feature model interface (#222)

* make variable declaration more concise

* add model interface

* optimize interface methods

* fix: go test failed

* warp returns

* optimize

tools/goctl/model/sql/util/slice.go

@@ -0,0 +1,12 @@
+package util
+
+func TrimStringSlice(list []string) []string {
+	var out []string
+	for _, item := range list {
+		if len(item) == 0 {
+			continue
+		}
+		out = append(out, item)
+	}
+	return out
+}