do not panic in init()

Instead return initDriver error from (Driver).Open.

Author: alexbrainman

conn.go

@@ -22,6 +22,10 @@ type Conn struct {
 var accessDriverSubstr = strings.ToUpper(strings.Replace("DRIVER={Microsoft Access Driver", " ", "", -1))
 
 func (d *Driver) Open(dsn string) (driver.Conn, error) {
+	if d.initErr != nil {
+		return nil, d.initErr
+	}
+
 	var out api.SQLHANDLE
 	ret := api.SQLAllocHandle(api.SQL_HANDLE_DBC, api.SQLHANDLE(d.h), &out)
 	if IsError(ret) {

driver.go

@@ -16,7 +16,8 @@ var drv Driver
 
 type Driver struct {
 	Stats
-	h api.SQLHENV // environment handle
+	h       api.SQLHENV // environment handle
+	initErr error
 }
 
 func initDriver() error {
@@ -72,7 +73,7 @@ func (d *Driver) Close() error {
 func init() {
 	err := initDriver()
 	if err != nil {
-		panic(err)
+		drv.initErr = err
 	}
 	sql.Register("odbc", &drv)
 }