Convert to time in Golang from milliseconds

Question

I have a some json data where there is a field called lastModifed contains time in millis. I wanted to convert this data into a struct type with json.UnMarshaller. I have mapped the field with json filed. But the conversion seems not working.

IE :

My Json looks like this:

{
   "name" : "hello",
   "lastModified" : 1438167001716
}

and struct Looks like

type Model struct {
    Name         string    `json:"name"`
    Lastmodified time.Time `json:"lastModified"`
}

looks not converting the time properly. how can i get the time from those millis??

NB: The millis of lastModifiedTime are getting from java System.currentTimeMillis();

Answer 1

In golang time.Time marshals to JSON using RFC3339, string representation. So you need to unmarshal your json using int64 instead of time.Time and convert after it by yourself:

type Model struct {
    Name   string `json:"name"`
    Millis int64  `json:"lastModified"`
}

func (m Model) Lastmodified() time.Time {
    return time.Unix(0, m.Millis * int64(time.Millisecond))
}

Go playground

Also you can use special wrapper above time.Time and override UnmarshalJSON there:

type Model struct {
    Name         string   `json:"name"`
    Lastmodified javaTime `json:"lastModified"`
}

type javaTime time.Time

func (j *javaTime) UnmarshalJSON(data []byte) error {
    millis, err := strconv.ParseInt(string(data), 10, 64)
    if err != nil {
        return err
    }
    *j = javaTime(time.Unix(0, millis * int64(time.Millisecond)))
    return nil
}

Go playground