// Option 1 (with await)
public async Task<AccountEntity> InsertAsync(AccountEntity item)
{
    using (var connection = _connectionFactory.GetConnection())
    {
        connection.Open();

        var sql = @"
INSERT INTO Account (UserName, Password)
OUTPUT INSERTED.*
VALUES (@UserName, @Password);";

        return await connection.QuerySingleAsync<AccountEntity>(sql, new { item.UserName, item.Password, });
    }
}