我正在通过下面的LoggerConfiguration创建一个自定义列。然后，使用中间件和我编写的UsernameColumnWriter类，我想在此列中打印发出请求时在PostgreSQL上登录的用户的名称。表和列正在形成，没有任何问题。但是，当我发出请求时，user_name列仍然为空，尽管创建了日志记录。
Serilog配置：

Logger log = new LoggerConfiguration()
.WriteTo.PostgreSQL(builder.Configuration.GetConnectionString("3pmConnectionString"),
    "Logs",
    needAutoCreateTable: true,
    columnOptions: new Dictionary<string, ColumnWriterBase>
    {
        {"message", new RenderedMessageColumnWriter(NpgsqlDbType.Text)},
        {"message_template", new MessageTemplateColumnWriter(NpgsqlDbType.Text)},
        {"level", new LevelColumnWriter(true , NpgsqlDbType.Varchar)},
        {"time_stamp", new TimestampColumnWriter(NpgsqlDbType.Timestamp)},
        {"exception", new ExceptionColumnWriter(NpgsqlDbType.Text)},
        {"log_event", new LogEventSerializedColumnWriter(NpgsqlDbType.Json)},
        {"user_name", new UsernameColumnWriter()}
    })
.WriteTo.Debug()
.WriteTo.Console()
.MinimumLevel.Information()
.CreateLogger();

builder.Host.UseSerilog(log);

中间件：

app.UseSerilogRequestLogging();
app.UseHttpLogging();

app.UseAuthentication();
app.UseAuthorization();

app.Use(async (context, next) => {
    var username = context.User?.Identity?.IsAuthenticated != null || true ? 
        context.User.Identity.Name : null;
    LogContext.PushProperty("user_name", username);
    await next();
});

我的班级：

public class UsernameColumnWriter : ColumnWriterBase {
        public UsernameColumnWriter() : base(NpgsqlDbType.Varchar) {
        }

        public override object GetValue(LogEvent logEvent, IFormatProvider formatProvider = null) {
        var (username, value) = logEvent.Properties.FirstOrDefault(p => p.Key == "user_name");
        return value?.ToString() ?? null;
    }
}