package api import ( "encoding/json" "errors" "time" ) type Duration time.Duration func (d *Duration) Duration() time.Duration { return time.Duration(*d) } func (d *Duration) MarshalJSON() ([]byte, error) { return json.Marshal(time.Duration(*d).String()) } func (d *Duration) UnmarshalJSON(b []byte) error { var v interface{} if err := json.Unmarshal(b, &v); err != nil { return err } switch value := v.(type) { case float64: *d = Duration(time.Duration(value)) return nil case string: tmp, err := time.ParseDuration(value) if err != nil { return err } *d = Duration(tmp) return nil default: return errors.New("invalid duration") } }