接口Interfaces

struct Dog {}
struct Cat {}

fn (d Dog) speak() string { 
    return 'woof'
} 

fn (c Cat) speak() string { 
    return 'meow' 
} 

interface Speaker {
    speak() string
}

fn perform(s Speaker) { 
    println(s.speak())
} 

dog := Dog{} 
cat := Cat{} 
perform(dog) // ==> "woof" 
perform(cat) // ==> "meow" 

类型通过实现其方法来实现接口。没有明确的意图声明，没有“implements”关键字。