optimize unit test & add document

tools/goctl/model/sql/gen/imports.go

@@ -2,17 +2,12 @@ package gen
 
 import (
 	"github.com/tal-tech/go-zero/tools/goctl/model/sql/template"
-	"github.com/tal-tech/go-zero/tools/goctl/util/templatex"
 )
 
-func genImports(withCache bool) (string, error) {
-	output, err := templatex.With("import").
-		Parse(template.Imports).
-		Execute(map[string]interface{}{
-			"withCache": withCache,
-		})
-	if err != nil {
-		return "", err
+func genImports(withCache bool) string {
+	if withCache {
+		return template.Imports
+	} else {
+		return template.ImportsNoCache
 	}
-	return output.String(), nil
 }