Go App Engine 数据存储：解决ID自动生成问题

package main

import (
    "context"
    "encoding/json"
    "fmt"
    "io/ioutil"
    "log"
    "net/http"

    "cloud.google.com/go/datastore"
)

// Participant 实体对象
type Participant struct {
    ID        int64  `datastore:"-" json:"ID"` // 忽略存储，用于JSON输出
    LastName  string `json:"LastName"`
    FirstName string `json:"FirstName"`
    Birthdate string `json:"Birthdate"`
    Email     string `json:"Email"`
    Cell      string `json:"Cell"`
}

func serveError(w http.ResponseWriter, err error) {
    log.Printf("Error: %v", err)
    http.Error(w, err.Error(), http.StatusInternalServerError)
}

func handleParticipant(client *datastore.Client, parentKey *datastore.Key) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        ctx := r.Context()

        switch r.Method {
        case "POST":
            d, err := ioutil.ReadAll(r.Body)
            if err != nil {
                serveError(w, err)
                return
            }

            participant := new(Participant)
            err = json.Unmarshal(d, &participant)
            if err != nil {
                serveError(w, err)
                return
            }

            // 创建 incomplete key
            key := datastore.NewIncompleteKey(ctx, "participant", parentKey)

            // 持久化数据
            putKey, err := client.Put(ctx, key, participant)
            if err != nil {
                serveError(w, err)
                return
            }

            // 获取新生成的 ID
            participant.ID = putKey.ID()

            // 从数据库中获取数据 (可选，验证数据)
            if err = client.Get(ctx, putKey, participant); err != nil {
                serveError(w, err)
                return
            }

            // 发送给消费者
            jsonData, err := json.Marshal(participant)
            if err != nil {
                serveError(w, err)
                return
            }
            w.Header().Set("Content-Type", "application/json")
            w.Write(jsonData)

        default:
            http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
        }
    }
}

func main() {
    ctx := context.Background()

    // 替换为你的项目 ID
    projectID := "your-project-id"

    client, err := datastore.NewClient(ctx, projectID)
    if err != nil {
        log.Fatalf("Failed to create client: %v", err)
    }
    defer client.Close()

    // 可选的 parent key
    var parentKey *datastore.Key = nil

    http.HandleFunc("/participant", handleParticipant(client, parentKey))

    port := "8080"
    log.Printf("Listening on port %s", port)
    if err := http.ListenAndServe(":"+port, nil); err != nil {
        log.Fatal(err)
    }
}