Go で JSON をアンマーシャリングするときに、RFC 3339 以外の時刻形式を処理するにはどうすればよいですか?

import (
    "fmt"
    "strconv"
    "strings"
    "time"

    "github.com/golang/protobuf/ptypes/timestamp"
)

type CustomTime struct {
    time.Time
}

const ctLayout = "2006/01/02|15:04:05"

func (ct *CustomTime) UnmarshalJSON(b []byte) (err error) {
    s := strings.Trim(string(b), "\"")
    if s == "null" {
        ct.Time = time.Time{}
        return
    }
    ct.Time, err = time.Parse(ctLayout, s)
    return
}

func (ct *CustomTime) MarshalJSON() ([]byte, error) {
    if ct.Time.IsZero() {
        return []byte("null"), nil
    }
    return []byte(fmt.Sprintf("\"%s\"", ct.Time.Format(ctLayout))), nil
}

var nilTime = (time.Time{}).UnixNano()

func (ct *CustomTime) IsSet() bool {
    return !ct.IsZero()
}

type Args struct {
    Time CustomTime
}

var data = `
    {"Time": "2014/08/01|11:27:18"}
`

func main() {
    a := Args{}
    if err := json.Unmarshal([]byte(data), &a); err != nil {
        fmt.Println("Error unmarshaling: ", err)
        return
    }

    if !a.Time.IsSet() {
        fmt.Println("Time not set")
    } else {
        fmt.Println(a.Time.String())
    }
}