You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: well_known_types.go
    path of file: ./repos/kratos/encoding/form
    
    the code of the file until where you have to start completion: package form

import (
	"encoding/base64"
	"fmt"
	"math"
	"strings"
	"time"

	"google.golang.org/protobuf/reflect/protoreflect"
)

const (
	// timestamp
	timestampMessageFullname    protoreflect.FullName    = "google.protobuf.Timestamp"
	maxTimestampSeconds                            
    
func marshalTimestamp(m protoreflect.Message) (string, error) {
	fds := m.Descriptor().Fields()
	fdSeconds := fds.ByNumber(timestampSecondsFieldNumber)
	fdNanos := fds.ByNumber(timestampNanosFieldNumber)

	secsVal := m.Get(fdSeconds)
	nanosVal := m.Get(fdNanos)
	secs := secsVal.Int()
	nanos := nanosVal.Int()
	if secs < minTimestampSeconds || secs > maxTimestampSeconds {
		return "", fmt.Errorf("%s: seconds out of range %v", timestampMessageFullname, secs)
	}
	if nanos < 0 || nanos > secondsInNanos {
		return "", fmt.Errorf("%s: nanos out of range %v", timestampMessageFullname, nanos)
	}
	// Uses RFC 3339, where generated output will be Z-normalized and uses 0, 3,
	// 6 or 9 fractional digits.
	t := time.Unix(secs, nanos).Local()
	x := t.Format("2006-01-02T15:04:05.000000000")
	x = strings.TrimSuffix(x, "000")
	x = strings.TrimSuffix(x, "000")
	x = strings.TrimSuffix(x, ".000")
	return x + "Z", nil
}