minimal code to reproduce https://github.com/terraform-providers/terraform-provider-google/issues/6377

service_account.go

package main

import (
	"context"
	"log"
	"time"

	"google.golang.org/api/iam/v1"
)

const (
	projectID            = "***"
	serviceAccountIDBase = "foobar"
)

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

	svc, err := iam.NewService(ctx)
	if err != nil {
		log.Fatal(err)
	}

	projectName := "projects/" + projectID

	for {
		log.Println("create")

		serviceAccountID := serviceAccountIDBase + time.Now().Format("20060102150405")

		r1, err := svc.Projects.ServiceAccounts.Create(projectName, &iam.CreateServiceAccountRequest{
			AccountId: serviceAccountID,
		}).Do()
		if err != nil {
			log.Fatal(err)
		}

		log.Println("created")

		name := r1.Name

		time.Sleep(1 * time.Second)

		log.Println("get")

		_, err = svc.Projects.ServiceAccounts.Get(name).Do()
		if err != nil {
			log.Fatal(err)
		}

		log.Println("got")

		log.Println("delete")

		_, err = svc.Projects.ServiceAccounts.Delete(name).Do()
		if err != nil {
			log.Fatal(err)
		}

		log.Printf("deleted %q", name)

		time.Sleep(1 * time.Second)
	}
}