func (i Int64) MustGet() int64 {
	if !i.Present() {
		panic("value not present")
	}
	return *i.value
}
MustGet returns the int64 value or panics if not present.
package optional
import (
	"encoding/json"
	"errors"
)
type Int64 struct {
	value *int64
}
func NewInt64(v int64) Int64 {
	return Int64{&v}
}
func (i *Int64) Set(v int64) {
	i.value = &v
}
func (i Int64) Get() (int64, error) {
	if !i.Present() {
		var zero int64
		return zero, errors.New("value not present")
	}
	return *i.value, nil
}