我正在嘗試創建一個連接到 Google Cloud API 的 Go RESTful API。發生了一個問題，描述為：無效操作：req.ParentId != nil（字符串和 nil 類型不匹配）在創建本地 API 之前，我設法編寫了一個 Go 模塊，該模塊可以連接、驗證和從 Google Cloud 提取數據。我現在正在將該模塊遷移為帶有路徑的 Restful API。該模塊的重點是獲取所有當前正在運行的虛擬機的列表。這是將其更改為restful API（有效）之前的模塊：package mainimport (    "fmt"    "example.com/compute"    "bytes")func main() {    buf := new(bytes.Buffer)    // Get a message and print it.    r.HandleFunc("/virtualmachines", ListAllInstances)    err := compute.ListAllInstances(buf, "unique-string-id")    if err != nil {        panic(err)    }    fmt.Println(buf.String()) // <======= Print buf contents!}// new file:package compute// [START compute_instances_list_all]import (    "context"    "fmt"    "io"    compute "cloud.google.com/go/compute/apiv1"    "google.golang.org/api/iterator"    computepb "google.golang.org/genproto/googleapis/cloud/compute/v1"    "google.golang.org/protobuf/proto")// listAllInstances prints all instances present in a project, grouped by their zone.func ListAllInstances(w io.Writer, projectID string) error {    // projectID := "your_project_id"    ctx := context.Background()    instancesClient, err := compute.NewInstancesRESTClient(ctx)    if err != nil {        return fmt.Errorf("NewInstancesRESTClient: %v", err)    }    defer instancesClient.Close()    // Use the `MaxResults` parameter to limit the number of results that the API returns per response page.    req := &computepb.AggregatedListInstancesRequest{        Project:    projectID,        MaxResults: proto.Uint32(6),    }    it := instancesClient.AggregatedList(ctx, req)    fmt.Fprintf(w, "Instances found:\n")    // Despite using the `MaxResults` parameter, you don't need to handle the pagination    // yourself. The returned iterator object handles pagination    // automatically, returning separated pages as you iterate over the results.ParentId是罪魁禍首（滾動下方查看完整錯誤）。我插入的字符串在上面的代碼中似乎不起作用。Google Cloud API 正在嘗試找出項目的父 ID。如何修復上面的代碼？