grpc中的.net Google.Cloud.Firestore名称解析错误

我的后端无法尝试访问云firestore集合。我使用nuget包Google.Cloud.Firestore（目前为1.0.0-beta20）。 错误是

Grpc.Core.RpcException: Status(StatusCode=Unavailable, Detail="Name resolution failure")

我的代码是

public async Task PushAppointment(CcAppointment appointment)
{
    var fireStoreDb = await FirestoreDb.CreateAsync("peakplan-fb-mobile"); 

    var docRef = fireStoreDb.Collection("appointments");  
    await docRef.AddAsync(appointment);
}

Google凭据JSON env var已正确设置和加载

我在异常消息之前获取这些日志：

D0530 02:26:56.253562 Grpc.Core.Internal.UnmanagedLibrary Attempting to load native library "/Users/gabrielwahle/.nuget/packages/grpc.core/1.19.0/lib/netstandard1.5/../../runtimes/osx/native/libgrpc_csharp_ext.x64.dylib"
D0530 02:26:56.347160 Grpc.Core.Internal.NativeExtension gRPC native library loaded successfully.

使用以下日志设置：

Environment.SetEnvironmentVariable("GRPC_TRACE", "api,cares_resolver,cares_address_sorting");
Environment.SetEnvironmentVariable("GRPC_VERBOSITY", "debug");

以前有人处理过这个错误吗