database/sql: close driver.Connector if it implements io.Closer

src/database/sql/driver/driver.go

@@ -115,6 +115,9 @@ type DriverContext interface {
 // DriverContext's OpenConnector method, to allow drivers
 // access to context and to avoid repeated parsing of driver
 // configuration.
+//
+// If a Connector implements io.Closer, the sql package's DB.Close
+// method will call Close and return error (if any).
 type Connector interface {
 	// Connect returns a connection to the database.
 	// Connect may return a cached connection (one previously

src/database/sql/fakedb_test.go

@@ -56,6 +56,7 @@ type fakeConnector struct {
 	name string
 
 	waiter func(context.Context)
+	closed bool
 }
 
 func (c *fakeConnector) Connect(context.Context) (driver.Conn, error) {
@@ -68,6 +69,14 @@ func (c *fakeConnector) Driver() driver.Driver {
 	return fdriver
 }
 
+func (c *fakeConnector) Close() error {
+	if c.closed {
+		return errors.New("fakedb: connector is closed")
+	}
+	c.closed = true
+	return nil
+}
+
 type fakeDriverCtx struct {
 	fakeDriver
 }

src/database/sql/sql.go

@@ -850,6 +850,12 @@ func (db *DB) Close() error {
 		}
 	}
 	db.stop()
+	if c, ok := db.connector.(io.Closer); ok {
+		err1 := c.Close()
+		if err1 != nil {
+			err = err1
+		}
+	}
 	return err
 }
 

src/database/sql/sql_test.go

@@ -4059,9 +4059,18 @@ func TestOpenConnector(t *testing.T) {
 	}
 	defer db.Close()
 
-	if _, is := db.connector.(*fakeConnector); !is {
+	c, ok := db.connector.(*fakeConnector)
+	if !ok {
 		t.Fatal("not using *fakeConnector")
 	}
+
+	if err := db.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	if !c.closed {
+		t.Fatal("connector is not closed")
+	}
 }
 
 type ctxOnlyDriver struct {