From 7d977c65095d6fa7251e7b4d178aac1bc3a4a642 Mon Sep 17 00:00:00 2001
From: Jean Mertz <jean@mertz.fm>
Date: Sat, 9 Jun 2018 19:18:09 +0200
Subject: [PATCH] Use the correct format for the message timestamp

As described in the Stackdriver documentation:

> A timestamp in RFC3339 UTC "Zulu" format, accurate to nanoseconds.
> Example: "2014-10-02T15:01:23.045123456Z".
---
 encoder.go      | 14 ++++++++++++--
 encoder_test.go | 13 +++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/encoder.go b/encoder.go
index 10145f4..eec571f 100644
--- a/encoder.go
+++ b/encoder.go
@@ -1,6 +1,10 @@
 package zapdriver
 
-import "go.uber.org/zap/zapcore"
+import (
+	"time"
+
+	"go.uber.org/zap/zapcore"
+)
 
 // logLevelSeverity maps the Zap log levels to the correct level names as
 // defined by Stackdriver.
@@ -37,7 +41,7 @@ var encoderConfig = zapcore.EncoderConfig{
 	StacktraceKey:  "stacktrace",
 	LineEnding:     zapcore.DefaultLineEnding,
 	EncodeLevel:    EncodeLevel,
-	EncodeTime:     zapcore.ISO8601TimeEncoder,
+	EncodeTime:     RFC3339NanoTimeEncoder,
 	EncodeDuration: zapcore.SecondsDurationEncoder,
 	EncodeCaller:   zapcore.ShortCallerEncoder,
 }
@@ -47,3 +51,9 @@ var encoderConfig = zapcore.EncoderConfig{
 func EncodeLevel(l zapcore.Level, enc zapcore.PrimitiveArrayEncoder) {
 	enc.AppendString(logLevelSeverity[l])
 }
+
+// RFC3339NanoTimeEncoder serializes a time.Time to an RFC3339Nano-formatted
+// string with nanoseconds precision.
+func RFC3339NanoTimeEncoder(t time.Time, enc zapcore.PrimitiveArrayEncoder) {
+	enc.AppendString(t.Format(time.RFC3339Nano))
+}
diff --git a/encoder_test.go b/encoder_test.go
index a28686a..dc9f87c 100644
--- a/encoder_test.go
+++ b/encoder_test.go
@@ -2,6 +2,7 @@ package zapdriver_test
 
 import (
 	"testing"
+	"time"
 
 	"github.com/blendle/zapdriver"
 	"github.com/stretchr/testify/assert"
@@ -35,3 +36,15 @@ func TestEncodeLevel(t *testing.T) {
 		})
 	}
 }
+
+func TestRFC3339NanoTimeEncoder(t *testing.T) {
+	t.Parallel()
+
+	ts := time.Date(2018, 4, 9, 12, 43, 12, 678359, time.UTC)
+
+	enc := &sliceArrayEncoder{}
+	zapdriver.RFC3339NanoTimeEncoder(ts, enc)
+
+	require.Len(t, enc.elems, 1)
+	assert.Equal(t, ts.Format(time.RFC3339Nano), enc.elems[0].(string))
+}