官网给的示例漏了引用部分“import go.mongodb.org/mongo-driver/mongo/readpref"
ctx, _ = context.WithTimeout(context.Background(), 2*time.Second)
err = client.Ping(ctx, readpref.Primary())
官网给的示例漏了引用部分“import go.mongodb.org/mongo-driver/mongo/readpref"
ctx, _ = context.WithTimeout(context.Background(), 2*time.Second)
err = client.Ping(ctx, readpref.Primary())