MINOR: [Go] Use shared cache in SQLite example. (apache#33983)

### Rationale for this change

When calling this server with a few concurrent requests, you can easily force the Go stdlib to spawn a new connection. Since only the `:memory:` DSN is specified, the stdlib doesn't know any better and effectively creates a new database. The result is a lot of `no such table` errors.

### What changes are included in this PR?

This change adds the `?cache=shared` as specified at:

https://www.sqlite.org/sharedcache.html#enabling_shared_cache_mode

This ensures that these new connections participate in same in-memory database and can see all the tables created at server start.

### Are these changes tested?

I haven't written any additional tests here, because this behavior is difficult to test. Suggestions are welcome on an approach here.

### Are there any user-facing changes?

No.

* Closes: apache#33983

Authored-by: Brett Buddin <[email protected]>
Signed-off-by: Matt Topol <[email protected]>

go/arrow/flight/flightsql/example/cmd/sqlite_flightsql_server/main.go

@@ -40,7 +40,13 @@ func main() {
 
 	flag.Parse()
 
-	srv, err := example.NewSQLiteFlightSQLServer()
+	db, err := example.CreateDB()
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer db.Close()
+
+	srv, err := example.NewSQLiteFlightSQLServer(db)
 	if err != nil {
 		log.Fatal(err)
 	}

go/arrow/flight/flightsql/example/sqlite_server.go

@@ -140,20 +140,8 @@ func prepareQueryForGetKeys(filter string) string {
 		` ORDER BY pk_catalog_name, pk_schema_name, pk_table_name, pk_key_name, key_sequence`
 }
 
-type Statement struct {
-	stmt   *sql.Stmt
-	params [][]interface{}
-}
-
-type SQLiteFlightSQLServer struct {
-	flightsql.BaseServer
-	db *sql.DB
-
-	prepared sync.Map
-}
-
-func NewSQLiteFlightSQLServer() (*SQLiteFlightSQLServer, error) {
-	db, err := sql.Open("sqlite", ":memory:")
+func CreateDB() (*sql.DB, error) {
+	db, err := sql.Open("sqlite", "file::memory:?cache=shared")
 	if err != nil {
 		return nil, err
 	}
@@ -178,10 +166,27 @@ func NewSQLiteFlightSQLServer() (*SQLiteFlightSQLServer, error) {
 	INSERT INTO intTable (keyName, value, foreignId) VALUES ('negative one', -1, 1);
 	INSERT INTO intTable (keyName, value, foreignId) VALUES (NULL, NULL, NULL);
 	`)
-
 	if err != nil {
+		db.Close()
 		return nil, err
 	}
+
+	return db, nil
+}
+
+type Statement struct {
+	stmt   *sql.Stmt
+	params [][]interface{}
+}
+
+type SQLiteFlightSQLServer struct {
+	flightsql.BaseServer
+	db *sql.DB
+
+	prepared sync.Map
+}
+
+func NewSQLiteFlightSQLServer(db *sql.DB) (*SQLiteFlightSQLServer, error) {
 	ret := &SQLiteFlightSQLServer{db: db}
 	ret.Alloc = memory.DefaultAllocator
 	for k, v := range SqlInfoResultMap() {

go/arrow/flight/flightsql/sqlite_server_test.go

@@ -21,6 +21,7 @@ package flightsql_test
 
 import (
 	"context"
+	"database/sql"
 	"os"
 	"strings"
 	"testing"
@@ -42,6 +43,7 @@ import (
 type FlightSqliteServerSuite struct {
 	suite.Suite
 
+	db  *sql.DB
 	srv *example.SQLiteFlightSQLServer
 	s   flight.Server
 	cl  *flightsql.Client
@@ -71,7 +73,9 @@ func (s *FlightSqliteServerSuite) SetupTest() {
 	var err error
 	s.mem = memory.NewCheckedAllocator(memory.DefaultAllocator)
 	s.s = flight.NewServerWithMiddleware(nil)
-	s.srv, err = example.NewSQLiteFlightSQLServer()
+	s.db, err = example.CreateDB()
+	s.Require().NoError(err)
+	s.srv, err = example.NewSQLiteFlightSQLServer(s.db)
 	s.Require().NoError(err)
 	s.srv.Alloc = s.mem
 
@@ -89,6 +93,8 @@ func (s *FlightSqliteServerSuite) TearDownTest() {
 	s.Require().NoError(s.cl.Close())
 	s.s.Shutdown()
 	s.srv = nil
+	err := s.db.Close()
+	s.Require().NoError(err)
 	s.mem.AssertSize(s.T(), 0)
 }