How to deal with date fields from JSON in a GO struct

I have a JSON content, with some date fields like "resolutiondate" and "created" and "updated" as shown below

{
   "expand":"names,schema",
   "startAt":0,
   "maxResults":50,
   "total":1,
   "issues":[
      {
         "expand":"operations,versionedRepresentations,editmeta,changelog,renderedFields",
         "id":"id",
         "self":"https://url1",
         "key":"key1",
         "fields":{
            "summary":"Summary-1",
            "customfield_10406":null,
		    "resolutiondate":"2021-06-10T10:07:35.000+0000",
            "created":"2021-06-10T10:05:24.000+0000",
            "description":"Description-1",
            ...
            ...
            ...
}

I am unmarshalling this JSON data into GO struct and saving the data in a excel sheet. Everything works as expected, the only issue is I'm defining the date fields as string datatypes in my GO struct, as below:

		Resolved           string `json:"resolutiondate,omitempty"`
		Created            string `json:"created,omitempty"`

Hence the final data saved in the excel file looks like:

But I want to save them as date datatype in the excel sheet, in a user defined format-mm/dd/yyyy. How can I effectively use the time package of Golang to achieve this ? Please help.

NOTE: I will be unable to share my complete code and the full JSON file.

For unmarshaling from custom format you need to create time.Time wrapper and implement json.Unmarshaler interface.

type CustomTime struct {
	time.Time
}

func (t *CustomTime) UnmarshalJSON(b []byte) (err error) {
	date, err := time.Parse(`"2006-01-02T15:04:05.000-0700"`, string(b))
	if err != nil {
		return err
	}
	t.Time = date
	return
}

Now specify your time fields as CustomTime

Resolved           CustomTime `json:"resolutiondate,omitempty"`
Created            CustomTime `json:"created,omitempty"`

For writting into excel you need to provide more info about your implementation.

But example solution:

func (t *CustomTime) ExcelDate() string {
	return t.Format("01/02/2006")
}

What you can do is, wrap string as your own custom type, and make it implement the Unmarshaler interface:

type Unmarshaler interface {
	UnmarshalJSON([]byte) error
}

Then take time coming with JSON and parse it to time.Time and format with your custom layout mm/dd/yyyy.

type Date string

func (d *Date) UnmarshalJSON(bytes []byte) error {
	dd, err := time.Parse(`"2006-01-02T15:04:05.000+0000"`, string(bytes))
	if err != nil{
		return err
	}
	*d = Date(dd.Format("01/02/2006"))

	return nil
}

Now you can use

Created            Date `json:"created,omitempty"`

inside your Go struct and unmarshal.

Run sample code here