Updating multiple values in DynamoDB with Go

I am trying to update both value1 and value2 item attributes in DynamoDb Table, but the UpdateExpression sets only one argument (value1). Trying to include both value1 and value2 (aws.String("set value1= :r, set value2= :c")) results in:

Got error calling UpdateItem: %s
ValidationException: Invalid UpdateExpression: Syntax error; token: "set", near: ", set 
HashValue" status code: 400, request id:******

How can I update more than one field in the Data Base item ?

--

func UpdateObject(obj MyObject) (string, error) {

sess := session.Must(session.NewSessionWithOptions(session.Options{
    SharedConfigState: session.SharedConfigEnable,
}))

// Create DynamoDB client
svc := dynamodb.New(sess)

// Update item in table Movies
tableName := "MyTable"

input := &dynamodb.UpdateItemInput{
    ExpressionAttributeValues: map[string]*dynamodb.AttributeValue{
        ":r": {
            N: aws.String(strconv.Itoa(obj.value1)),
        },
        ":c": {
            S: aws.String(obj.value2),
        },
    },
    TableName: aws.String(tableName),
    Key: map[string]*dynamodb.AttributeValue{
        "ThreatID": {
            N: aws.String(strconv.Itoa(obj.value3)),
        },
        "ThreatName": {
            S: aws.String(obj.value4),
        },
    },
    ReturnValues:     aws.String("UPDATED_NEW"),
    UpdateExpression: aws.String("set value1= :r"),
}

 //........

}

--

 type MyObject struct {
     value3 int
     value4 string
     value2 string
     value1 int
   }