Linq2db doesn't support read numeric into BigInteger

Describe your issue

While reading entity with BigInteger property (dbtype - numeric(78,0)) - linq2db throws exception

Exception message: System.OverflowException: Numeric value does not fit in a System.Decimal
Stack trace: System.OverflowException: Numeric value does not fit in a System.Decimal
   at Npgsql.Internal.TypeHandlers.NumericHandlers.NumericHandler.Read(NpgsqlReadBuffer buf, Int32 len, Boolean async, FieldDescription fieldDescription)
   at Npgsql.NpgsqlDataReader.GetFieldValue[T](Int32 ordinal)
   at Npgsql.NpgsqlDataReader.GetDecimal(Int32 ordinal)
   at lambda_method56(Closure, IQueryRunner, DbDataReader)
   at LinqToDB.Linq.QueryRunner.Mapper`1.Map(IDataContext context, IQueryRunner queryRunner, DbDataReader dataReader, ReaderMapperInfo& mapperInfo)
   at LinqToDB.Linq.QueryRunner.ExecuteQueryAsync[T](Query query, IDataContext dataContext, Mapper`1 mapper, Expression expression, Object[] ps, Object[] preambles, Int32 queryNumber, Func`2 func, TakeSkipDelegate skipAction, TakeSkipDelegate takeAction, CancellationToken cancellationToken)
   at LinqToDB.Linq.QueryRunner.ExecuteQueryAsync[T](Query query, IDataContext dataContext, Mapper`1 mapper, Expression expression, Object[] ps, Object[] preambles, Int32 queryNumber, Func`2 func, TakeSkipDelegate skipAction, TakeSkipDelegate takeAction, CancellationToken cancellationToken)
   at LinqToDB.Linq.QueryRunner.ExecuteQueryAsync[T](Query query, IDataContext dataContext, Mapper`1 mapper, Expression expression, Object[] ps, Object[] preambles, Int32 queryNumber, Func`2 func, TakeSkipDelegate skipAction, TakeSkipDelegate takeAction, CancellationToken cancellationToken)
   at LinqToDB.Linq.Builder.FirstSingleBuilder.FirstSingleContext.<>c__DisplayClass4_0`1.<<GetFirstOrDefaultElement>b__1>d.MoveNext()
--- End of stack trace from previous location ---
   at LinqToDB.Linq.ExpressionQuery`1.LinqToDB.Async.IQueryProviderAsync.ExecuteAsync[TResult](Expression expression, CancellationToken cancellationToken)
   at Domain.Services.FundsTransferService.TransferAsync(String senderAddress, String recipientAddress, BigInteger amount) in 

Steps to reproduce

var transfer = await connection.Transfers.FirstOrDefaultAsync();

builder.Entity<Transfer>()
            .HasPrimaryKey(x => x.Id)
            .Property(x => x.Amount).HasPrecision(78).HasScale(0);

Environment details

Linq To DB version: 5.0.0

Database (with version): Postgres

[MaceWindu]

My bad, should be:

SetProviderField<DbDataReader, BigInteger, decimal>((DbDataReader rd, int idx) => rd.GetFieldValue<BigInteger>(idx));

[twilightrus]

My bad, should be:

SetProviderField<DbDataReader, BigInteger, decimal>((DbDataReader rd, int idx) => rd.GetFieldValue<BigInteger>(idx));

Solved, thanks!