stub.go

package main

import (
	"fmt"
	"reflect"
	"time"
)

func main() {
	stubPrototype := func(in []reflect.Value) []reflect.Value {
		return []reflect.Value{reflect.ValueOf(time.Now())}
	}

	makeStub := func(stubbed interface{}) interface{} {
		return reflect.MakeFunc(reflect.TypeOf(stubbed), stubPrototype).Interface()
	}

	timeStub := makeStub(time.Now).(func() time.Time)
	fmt.Println(timeStub())
}