finish upstream subcommand

utils/output_utils.go

@@ -3,13 +3,22 @@ package utils
 import (
 	"encoding/json"
 	"fmt"
+	"io/ioutil"
 )
 
-func OutputJSON(data map[string][]string) {
+func OutputJSON(data interface{}, filename string) error {
 	jsonstr, err := json.MarshalIndent(data, "", "    ")
 	if err != nil {
 		fmt.Println("JSON encoding error:", err)
-		return
+		return err
 	}
-	fmt.Println(string(jsonstr))
+	if filename == "-" {
+		fmt.Println(string(jsonstr))
+	} else {
+		err := ioutil.WriteFile(filename, jsonstr, 0666)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
 }