I have researched the popular `sql` packages and found that almost none of them have a feature to throw an error when the connection is lost. For example, in `nodejs`'s mysql package, we can use `connection.on('error')` to listen for errors.

However, in Golang (at least in several popular packages), there is no similar functionality. It is not difficult to understand when you delve deeper.

> The sql package creates and frees connections automatically; it also maintains a free pool of idle connections. If the database has a concept of per-connection state, such state can be reliably observed within a transaction (Tx) or connection (Conn). Once DB.Begin is called, the returned Tx is bound to a single connection. Once Commit or Rollback is called on the transaction, that transaction's connection is returned to DB's idle connection pool. The pool size can be controlled with SetMaxIdleConns.

In simple terms, when you call `sql.Open`, it does not actually establish a connection but internally maintains a connection pool and tries to connect when needed. This means that if you encounter a connection loss due to network issues while performing a query, `database/sql` will attempt to retry for you at the underlying level.

This can be considered a good thing as you don't have to handle the retry logic yourself. However, sometimes you may want to know about the connection loss before executing a query. I hope the entire application can be aware of this before that.

If you want to achieve something similar, you need to modify the underlying Dialer logic to notify your program immediately when the network is disconnected.