Print value from Golang custom strcu

Question

I am new to Golang. I have below code, Can someone please help to Print Only ID from the custom created struct?

type Currency struct {
    ID        uint         `db:"id" json:"id"`
    Name      string       `db:"name" json:"name"`
    Code      string       `db:"code" json:"code"`
    CreatedAt sql.NullTime `db:"createdAt" json:"createdAt"`
    UpdatedAt sql.NullTime `db:"updatedAt" json:"updatedAt"`
}

type temp struct {
    Currency map[string]Currency
}

func GetCurrencies(db *sqlx.DB) ([]Currency, error) {
    sqlStatement := `SELECT * FROM "Currencies"`
    var currencyRows []Currency
    err := db.Select(&currencyRows, sqlStatement)
    return currencyRows, err
}

func PrintC(db *sqlx.DB) {

    Currencies, _ := GetCurrencies(db)
    stores := []temp{}
    for _, currency := range Currencies {
        store := temp{
            Currency: map[string]Currency{
                currency.Name: {
                    ID:        currency.ID,
                    Name:      currency.Name,
                    Code:      currency.Code,
                    CreatedAt: currency.CreatedAt,
                    UpdatedAt: currency.UpdatedAt,
                },
            },
        }
        stores = append(stores, store)
    }

  fmt.Println(stores)

}

Current Output:

[{map[Ethereum:{2 Ethereum ETH {2022-02-03 14:10:58.264 +0000 UTC true} {2022-02-03 14:10:58.264 +0000 UTC true}}]} {map[Bitcoin:{1 Bitcoin BTC {2022-02-03 14:10:59.471 +0000 UTC true} {2022-02-03 14:10:59.471 +0000 UTC true}}]}]

Expected Output:

// PRINT ONLY ETHEREUM ID // PRINT ONLY BITCOIN ID

Answer 1

You can implement Stringer interface and define the way how would you like to print out your struct. https://go.dev/tour/methods/17

Answer 2

This snippet bellow implements the Stringer interface which is required by the fmt package. Basically the fmt package look for this interface to print values.

func (cr Currency) String() string {
    return fmt.Sprintf("%v", cr.ID)
}