如何在同一包中的另一个类中使用一个类？

I'm fairly new to Go and I'm making an a small flashcards app. My package structure is this

VocabHelper
|
-|src
--|com
---|wks
----|card
------Card.go
------Deck.go
----|main
------main.go

Deck and Card are two separate classes but they're in the same package:

Card.go

package card

type Card struct{

    Question string
    Answer string

}

Deck.go

package card

import (
    "math/rand"
)

type Deck struct{

    Cards []card.Card

}

When I try to compile the project, the compiler says undefined:card even though card is in the same package as deck. How can I use the card class in the deck class?

Leave off the card. part, and it should work. They're both in the same package.

type Deck struct{
   Cards []Card
}