test_custom_time_unmarshal.go

// UnmarshalJSON from string to time.Time
package main

import (
	"encoding/json"
	"fmt"
	"time"
)

type Response struct {
	Time CustomTime
}

type CustomTime struct {
	time.Time
}

func (t *CustomTime) UnmarshalJSON(b []byte) error {
	var timeString string
	err := json.Unmarshal(b, &timeString)
	if err != nil {
		// fmt.Println(err.Error())
		return err
	}
	// RFC3339     = "2006-01-02T15:04:05Z07:00"
	t2, err := time.Parse("2006-01-02T15:04:05", timeString)
	if err != nil {
		// fmt.Println(err.Error())
		return err
	}
	t.Time = t2

	return nil
}

func main() {
	data := []byte(`{"Time":"2017-10-20T00:00:00"}`)

	res := new(Response)
	err := json.Unmarshal(data, &res)
	if err != nil {
		fmt.Printf(err.Error())
	} else {
		fmt.Printf("%v\n", res)
	}
}