golang json怎么隐藏某个字段

type RealTimeData struct {
    Code           string   `json:"code"`
    Time           time.Time    `json:"time"`
    OpenPrice      float32  `json:"openPrice"`
    PrevClosePrice float32  `json:"prevClosePrice"`
    LastPrice      float32  `json:"lastPrice"`
    HighPrice      float32  `json:"highPrice"`
    LowPrice       float32  `json:"lowPrice"`
    MarketValue    float32  `json:"marketValue"`
    PER            float32  `json:"per"`    // static price/earning ration
    PBR            float32  `json:"pbr"` // price/book ration
    DataSource     string}

DataSource     string   `json:"-"`