improved docs

docs/QuickStart.md

@@ -91,7 +91,7 @@ f, err := os.Create("sql.log")
 		println(err.Error())
 		return
 	}
-engine.Logger = f
+engine.Logger = xorm.NewSimpleLogger(f)
 ```
 
 3.Engine provide DB connection pool settings.

docs/QuickStartCN.md

@@ -95,7 +95,7 @@ f, err := os.Create("sql.log")
 		println(err.Error())
 		return
 	}
-engine.Logger = f
+engine.Logger = xorm.NewSimpleLogger(f)
 ```
 
 3.engine内部支持连接池接口。

xorm.go

@@ -1,7 +1,6 @@
 package xorm
 
 import (
-	"database/sql"
 	"errors"
 	"fmt"
 	"os"
@@ -17,13 +16,7 @@ const (
 	Version string = "0.4"
 )
 
-// !nashtsai! implicit register drivers and dialects is no good, as init() can be called before sql driver got registered
-// func init() {
-// 	regDrvsNDialects()
-// }
-
 func regDrvsNDialects() bool {
-	if core.RegisteredDriverSize() == 0 {
 	providedDrvsNDialects := map[string]struct {
 		dbType     core.DbType
 		getDriver  func() core.Driver
@@ -40,19 +33,12 @@ func regDrvsNDialects() bool {
 	}
 
 	for driverName, v := range providedDrvsNDialects {
-			_, err := sql.Open(driverName, "")
-			if err == nil {
-				// fmt.Printf("driver succeed: %v\n", driverName)
+		if driver := core.QueryDriver(driverName); driver == nil {
 			core.RegisterDriver(driverName, v.getDriver())
 			core.RegisterDialect(v.dbType, v.getDialect())
-			} else {
-				// fmt.Printf("driver failed: %v | err: %v\n", driverName, err)
 		}
 	}
 	return true
-	} else {
-		return false
-	}
 }
 
 func close(engine *Engine) {