How do I set up a DSN connection string for a Databricks SQL warehouse using the sql.Open() function in Go, and what are some optional parameters I can use to customize the connection?
To set up a DSN connection string for a Databricks SQL warehouse using the `sql.Open()` function in Go, you can follow the example provided in the documentation:

```go
package main

import (
	"database/sql"
	"os"

	_ "github.com/databricks/databricks-sql-go"
)

func main() {
	dsn := os.Getenv("DATABRICKS_DSN")
	if dsn == "" {
		panic("No connection string found. " +
			"Set the DATABRICKS_DSN environment variable, and try again.")
	}

	db, err := sql.Open("databricks", dsn)
	if err!= nil {
		panic(err)
	}
	defer db.Close()

	if err := db.Ping(); err!= nil {
		panic(err)
	}
}
```

In this example, the DSN connection string is retrieved from an environment variable named `DATABRICKS_DSN`. The format of the DSN connection string should be:

```
token:<personal-access-token>@<server-hostname>:<port-number>/<http-path>?<param1=value1>&<param2=value2>
```

For a SQL warehouse, the connection string might look like this:

```
token:dapi12345678901234567890123456789012@dbc-a1b2345c-d6e7.cloud.databricks.com:443/sql/1.0/endpoints/a1b234c5678901d2
```

There are several optional parameters that you can use to customize the connection. Some of the more frequently used ones include:

* `catalog`: Sets the initial catalog name in the session.
* `schema`: Sets the initial schema name in the session.
* `maxRows`: Sets up the maximum number of rows fetched per request. The default is 10000.
* `timeout`: Adds the timeout (in seconds) for the server query execution. The default is no timeout.
* `userAgentEntry`: Used to identify partners. For more information, see your partner’s documentation.

These parameters can be specified in the DSN connection string as follows:

```
token:dapi12345678901234567890123456789012@dbc-a1b2345c-d6e7.cloud.databricks.com:443/sql/1.0/endpoints/a1b234c5678901d2?catalog=hive_metastore&schema=example&maxRows=100&timeout=60&timezone=America/Sao_Paulo&ansi_mode=true
```

In addition to these optional parameters, there are also supported optional session parameters that can be specified in the DSN connection string. Some of the more frequently used ones include:

* `ansi_mode`: A Boolean string. true for session statements to adhere to rules specified by the ANSI SQL specification. The system default is false.
* `timezone`: A string, for example America/Los_Angeles. Sets the timezone of the session. The system default is UTC.

These session parameters can be specified in the DSN connection string as follows:

```
token:dapi12345678901234567890123456789012@dbc-a1b2345c-d6e7.cloud.databricks.com:443/sql/1.0/endpoints/a1b234c5678901d2?catalog=hive_metastore&schema=example&maxRows=100&timeout=60&timezone=America/Sao_Paulo&ansi_mode=true
```