optimize the performance of the function appendFormatRFC3339

Author: fx408

src/time/format_rfc3339.go

@@ -53,6 +53,13 @@ func (t Time) appendFormatRFC3339(b []byte, nanos bool) []byte {
 		b = append(b, '+')
 	}
 
+	if zone > 3600 {
+		b = appendInt(b, zone/60, 2)
+		b = append(b, ':')
+		b = appendInt(b, zone%60, 2)
+		return b
+	}
+
 	zone %= 3600
 	b = append(b,
 		tensDigit[zone/60], onesDigit[zone/60],

src/time/format_test.go

@@ -1123,6 +1123,7 @@ func BenchmarkAppendIntWidth4(b *testing.B) {
 func BenchmarkTimeFormatRFC3339(b *testing.B) {
 	tm := Unix(1661201140, 676836973)
 	buf := make([]byte, 0, 64)
+	b.ReportAllocs()
 	for b.Loop() {
 		buf = tm.AppendFormat(buf[:0], RFC3339)
 	}