对 Npgsql 进行的二次封装，包含连接池、事务、缓存、读写分离
也是dotnetgen_postgresql生成器所需postgresql数据库基础封装
https://github.com/2881099/dotnetGen_postgresql
Install-Package dng.Pgsql
public static Npgsql.Executer PgsqlInstance =
new Npgsql.Executer(IDistributedCache, masterConnectionString, slaveConnectionStrings, ILogger);
PgsqlInstance.ExecuteReader
PgsqlInstance.ExecuteReaderAsync
PgsqlInstance.ExecuteArray
PgsqlInstance.ExecuteArrayAsync
PgsqlInstance.ExecuteNonQuery
PgsqlInstance.ExecuteNonQueryAsync
PgsqlInstance.ExecuteScalar
PgsqlInstance.ExecuteScalarAsyncPgsqlInstance.Transaction(() => {
});PgsqlInstance.CacheShell(key, timeoutSeconds, () => {
return dataSource;
});
PgsqlInstance.RemoveCache(key);若配置了从数据库连接串，从数据库可以设置多个，访问策略为随机。从库实现了故障切换，自动恢复机制。
以下方法执行 sql 语句，为 select 开头，则默认查从数据库，反之则查主数据库。
PgsqlInstance.ExecuteReader
PgsqlInstance.ExecuteReaderAsync
PgsqlInstance.ExecuteArray
PgsqlInstance.ExecuteArrayAsync以下方法在主数据库执行：
PgsqlInstance.ExecuteNonQuery
PgsqlInstance.ExecuteNonQueryAsync
PgsqlInstance.ExecuteScalar
PgsqlInstance.ExecuteScalarAsync