我有下面的Go语言示例代码，它将来自REST请求（GIN）的数据插入MongoDB，但是它失败了，并显示：

['timestamp' must be present and contain a valid BSON UTC datetime value]

代码：

func CreateDevicesReadings(c *gin.Context) {

var devicesReadings DevicesReadings
c.BindJSON(&devicesReadings)

// Connect to MongoDB
client, err := mongo.Connect(context.Background(), clientOptions)
if err != nil {
    c.JSON(500, gin.H{
        "message": "Internal Server Error. Could not connect to the database.",

    })
    log.Default().Println(err)
}

collection := client.Database("florly").Collection("devicesReadings")
ctx, _ := context.WithTimeout(context.Background(), 5*time.Second)

// Set timestamp to the current time at the moment of the request
for i := 0; i < len(devicesReadings.DevicesReadings); i++ {
    devicesReadings.DevicesReadings[i].Timestamp = time.Now().UTC()
} 
_, err = collection.InsertOne(ctx, devicesReadings)
if err != nil {
    c.JSON(500, gin.H{
        "message": "Internal Server Error. Could not insert the data into the database.",
    })
    log.Default().Println(err)
} else {
    log.Default().Println("Data inserted successfully.")
}

client.Disconnect(context.Background())
}

type DeviceReadings struct {
    ID      primitive.ObjectID `json:"_id,omitempty" bson:"_id,omitempty"`
    Alias          string `json:"alias" bson:"alias"`
    Timestamp   time.Time `json:"timestamp,omitempty" bson:"timestamp"`
    SystemReadings SystemReadings `json:"systemReadings" bson:"systemReadings"`
    SensorReadings SensorReadings `json:"sensorsReadings" bson:"sensorsReadings"`
}

我做错了什么？我以为Mongodb完成了将time.time类型转换为MongoDB所需类型的整个过程。