如何定制json序列化

Marshal traverses the value v recursively.

• If an encountered value implements the Marshaler interface and is not a nil pointer, Marshal calls its MarshalJSON method to produce JSON.

• If no MarshalJSON method is present but the value implements encoding.TextMarshaler instead, Marshal calls its MarshalText method and encodes the result as a JSON string

也就是说，对于自定义类型，要支持json序列化，要实现以下接口：

type Marshaler interface {
    MarshalJSON() ([]byte, error)
}
    
type TextMarshaler interface {
    MarshalText() (text []byte, err error)
}