add millisecond duration encoder

make ms encoder compatible for go version <=1.13.0 & add testcase for ms encoder

change name of ms encoder

zapcore/encoder.go

@@ -168,6 +168,12 @@ func NanosDurationEncoder(d time.Duration, enc PrimitiveArrayEncoder) {
 	enc.AppendInt64(int64(d))
 }
 
+// MillisDurationEncoder serializes a time.Duration to an integer number of
+// milliseconds elapsed.
+func MillisDurationEncoder(d time.Duration, enc PrimitiveArrayEncoder) {
+	enc.AppendInt64(d.Nanoseconds() / 1e6)
+}
+
 // StringDurationEncoder serializes a time.Duration using its built-in String
 // method.
 func StringDurationEncoder(d time.Duration, enc PrimitiveArrayEncoder) {
@@ -183,6 +189,8 @@ func (e *DurationEncoder) UnmarshalText(text []byte) error {
 		*e = StringDurationEncoder
 	case "nanos":
 		*e = NanosDurationEncoder
+	case "ms":
+		*e = MillisDurationEncoder
 	default:
 		*e = SecondsDurationEncoder
 	}

zapcore/encoder_test.go

@@ -566,6 +566,7 @@ func TestDurationEncoders(t *testing.T) {
 	}{
 		{"string", "1.0000005s"},
 		{"nanos", int64(1000000500)},
+		{"ms", int64(1000)},
 		{"", 1.0000005},
 		{"something-random", 1.0000005},
 	}