在gorilla websocket库中使用golang，为什么WriteJson会返回错误？

package main

import (
    "encoding/json"
    "log"
    "net/http"
    "time"

    "github.com/gorilla/websocket"
)

var upgrader = websocket.Upgrader{
    ReadBufferSize:  1024,
    WriteBufferSize: 1024,
}

type MyData struct {
    Name string `json:"name"`
    Age  int    `json:"age"`
}

func handler(w http.ResponseWriter, r *http.Request) {
    conn, err := upgrader.Upgrade(w, r, nil)
    if err != nil {
        log.Println("Upgrade:", err)
        return
    }
    defer conn.Close()

    data := MyData{Name: "Alice", Age: 30}

    for {
        err := conn.WriteJSON(data)
        if err == nil {
            break
        }
        if websocket.IsWriteBlocking(err) {
            time.Sleep(100 * time.Millisecond)
        } else {
            log.Println("WriteJSON:", err)
            break
        }
    }
}

func main() {
    http.HandleFunc("/ws", handler)
    log.Fatal(http.ListenAndServe(":8080", nil))
}