add message.Time()

message.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"strings"
+	"time"
 )
 
 type Message struct {
@@ -23,6 +24,10 @@ func (m Message) Empty() bool {
 	return m == (Message{})
 }
 
+func (m Message) Time() time.Time {
+	return time.Unix(int64(m.TS), 0)
+}
+
 func (m Message) Serialize() []byte {
 	b, err := json.Marshal(m)
 	if err != nil {

message_test.go

@@ -107,6 +107,9 @@ func TestParseSlackTestdata(t *testing.T) {
 				if got != want.message {
 					t.Errorf("wanted \n\t%+v, got\n\t%+v", want.message, got)
 				}
+				if time := got.Time(); time.Unix() != int64(got.TS) {
+					t.Error("not unix time", got.TS, time)
+				}
 			})
 		})
 	}