From 2311d04cabea8f0232a77b8bc5ed7a6403b336f6 Mon Sep 17 00:00:00 2001
From: Daryl Ng <daryl.n.w.k@gmail.com>
Date: Thu, 2 Apr 2020 16:10:18 +0800
Subject: [PATCH] Handle time.Time to unmarshal to TimeFormat

---
 flatten.go      | 12 +++++++++++-
 flatten_test.go |  8 ++++++--
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/flatten.go b/flatten.go
index d3d6f4c..1cef66f 100644
--- a/flatten.go
+++ b/flatten.go
@@ -4,8 +4,13 @@ import (
 	"log"
 	"reflect"
 	"strings"
+	"time"
 )
 
+// TimeFormat defines default time format when unmarshalling time.Time
+// Override this to unmarshal time.Time to a different format
+var TimeFormat = time.RFC3339Nano
+
 // Struct parses a struct `s` with JSON tags and flattens nested parameters
 // to only one level and passes the result to `m`.
 func Struct(s interface{}, m map[string]interface{}) {
@@ -33,7 +38,12 @@ func flatten(key string, s interface{}, m map[string]interface{}) {
 
 		switch reflect.ValueOf(val.Field(i).Interface()).Kind() {
 		case reflect.Struct:
-			flatten(tag, val.Field(i).Interface(), m)
+			switch val.Field(i).Interface().(type) {
+			case time.Time:
+				m[tag] = val.Field(i).Interface().(time.Time).Format(TimeFormat)
+			default:
+				flatten(tag, val.Field(i).Interface(), m)
+			}
 		default:
 			if !reflect.DeepEqual(val.Field(i).Interface(), reflect.Zero(val.Field(i).Type()).Interface()) {
 				m[tag] = val.Field(i).Interface()
diff --git a/flatten_test.go b/flatten_test.go
index 1a74c27..5a2d94c 100644
--- a/flatten_test.go
+++ b/flatten_test.go
@@ -2,6 +2,7 @@ package flatten_test
 
 import (
 	"testing"
+	"time"
 
 	"github.com/darylnwk/flatten"
 	"github.com/stretchr/testify/assert"
@@ -16,6 +17,7 @@ type FooBar struct {
 	Foo          string       `json:"foo"`
 	Bar          string       `json:"bar"`
 	NestedFooBar NestedFooBar `json:"nested"`
+	Time         time.Time    `json:"time"`
 }
 
 func TestFlatten(t *testing.T) {
@@ -27,8 +29,9 @@ func TestFlatten(t *testing.T) {
 	}, m)
 
 	assert.Equal(t, map[string]interface{}{
-		"foo": "foo",
-		"bar": "bar",
+		"foo":  "foo",
+		"bar":  "bar",
+		"time": "0001-01-01T00:00:00Z",
 	}, m)
 }
 
@@ -49,5 +52,6 @@ func TestFlatten_Nested(t *testing.T) {
 		"bar":        "bar",
 		"nested.foo": "foo",
 		"nested.bar": "bar",
+		"time":       "0001-01-01T00:00:00Z",
 	}, m)
 }