我在尝试从postgressql获取数据时遇到了一个问题。我正在使用.NET Core 5.0和postgressql作为我的数据库解决方案的微服务架构。
我正在尝试使用Docker容器来容器化我的应用程序，一切都很好，直到我尝试通过API获取一些数据。
我得到了这种类型的错误：

Npgsql.PostgresException (0x80004005): 28P01: password authentication failed for user "admin"
   at Npgsql.NpgsqlConnector.<ReadMessage>g__ReadMessageLong|194_0(NpgsqlConnector connector, Boolean async, DataRowLoadingMode dataRowLoadingMode, Boolean readingNotifications, Boolean isReadingPrependedMessage)
   at Npgsql.NpgsqlConnector.AuthenticateMD5(String username, Byte[] salt, Boolean async, CancellationToken cancellationToken)
   at Npgsql.NpgsqlConnector.Authenticate(String username, NpgsqlTimeout timeout, Boolean async, CancellationToken cancellationToken)
   at Npgsql.NpgsqlConnector.Open(NpgsqlTimeout timeout, Boolean async, CancellationToken cancellationToken)
   at Npgsql.ConnectorPool.OpenNewConnector(NpgsqlConnection conn, NpgsqlTimeout timeout, Boolean async, CancellationToken cancellationToken)
   at Npgsql.ConnectorPool.<>c__DisplayClass38_0.<<Rent>g__RentAsync|0>d.MoveNext()
--- End of stack trace from previous location ---
   at Npgsql.NpgsqlConnection.<>c__DisplayClass41_0.<<Open>g__OpenAsync|0>d.MoveNext()
--- End of stack trace from previous location ---
   at Dapper.SqlMapper.QueryRowAsync[T](IDbConnection cnn, Row row, Type effectiveType, CommandDefinition command) in /_/Dapper/SqlMapper.Async.cs:line 472

从后端的Angular 来看，我尝试按productName获取数据的情况非常简单：

public async Task<Coupon> GetDiscount(string productName)
    {
        using var connection = new NpgsqlConnection
            (_configuration.GetValue<string>("DatabaseSettings:ConnectionString"));

        var coupon = await connection.QueryFirstOrDefaultAsync<Coupon>
            ("SELECT * FROM Coupon WHERE ProductName = @ProductName", new { ProductName = productName });

        if (coupon == null)
            return new Coupon 
            { ProductName = "No Discount", Amount = 0, Description = "No Discount Desc" };

        return coupon;
    }

我的appsettings.json文件，或者更准确地说是指向postgressql的连接字符串是这样的：

"DatabaseSettings": {
    "ConnectionString": "Server=localhost;Port=5432;Database=DiscountDb;User Id=admin;Password=admin1234;"
  },

在Docker撰写覆盖yml文件中，我有：

discountdb:
    container_name: discountdb
    environment:
      - POSTGRES_USER=admin
      - POSTGRES_PASSWORD=admin1234
      - POSTGRES_DB=DiscountDb
    restart: always
    ports:
        - "5432:5432"
    volumes:
      - postgres_data:/var/lib/postgresql/data/

正如我所看到的，在我的portainer中，我可以看到discountdb已经启动并正在运行

我错过了什么我不知道是什么。