我有以下接口和一些實現(xiàn)它的結(jié)構(gòu)：package mainimport "fmt"type vehicle interface {    vehicleType() string    numberOfWheels() int    EngineType() string}// -------------------------------------------type truck struct {    loadCapacity int}func (t truck) vehicleType() string {    return "Truck"}func (t truck) numberOfWheels() int {    return 6}func (t truck) EngineType() string {    return "Gasoline"}// -------------------------------------------type ev struct {    capacityInKWh int}func (e ev) vehicleType() string {    return "Electric Vehicle"}func (e ev) numberOfWheels() int {    return 4}func (e ev) EngineType() string {    return "Electric"}func (e ev) Capacity() int {    return e.capacityInKWh}// -------------------------------------------type dealer struct{}func (d dealer) sell(automobile vehicle) {    fmt.Println("Selling a vehicle with the following properties")    fmt.Printf("Vehicle Type: %s \n", automobile.vehicleType())    fmt.Printf("Vehicle Number of wheels: %d \n", automobile.numberOfWheels())    fmt.Printf("Vehicle Engine Type: %s \n", automobile.EngineType())    if automobile.EngineType() == "Electric" {        fmt.Printf("The battery capacity of the vehicle is %d KWh", automobile.Capacity())        //fmt.Printf("Here")    }}func main() {    volvoTruck := truck{        loadCapacity: 10,    }    tesla := ev{        capacityInKWh: 100,    }    myDealer := dealer{}    myDealer.sell(volvoTruck)    fmt.Println("---------------------------")    myDealer.sell(tesla)}Sell我的dealer{}結(jié)構(gòu)中的方法接收一個接口。在這個方法中，我想調(diào)用一個只存在于實現(xiàn)接口的結(jié)構(gòu)之一上而不存在于其他結(jié)構(gòu)上的方法：if automobile.EngineType() == "Electric" {            fmt.Printf("The battery capacity of the vehicle is %d KWh", automobile.Capacity())        }請注意，Capacity()它只存在于ev{}而不存在于 中truck{}。有沒有辦法做到這一點，而不必將此方法添加到強制所有實現(xiàn)使用它的接口？