Use log.PrintX instead of fmt.PrintX (go-gorm#1634)

callback.go

@@ -1,8 +1,6 @@
 package gorm
 
-import (
-	"fmt"
-)
+import "log"
 
 // DefaultCallback default callbacks defined by gorm
 var DefaultCallback = &Callback{}
@@ -95,7 +93,7 @@ func (cp *CallbackProcessor) Before(callbackName string) *CallbackProcessor {
 func (cp *CallbackProcessor) Register(callbackName string, callback func(scope *Scope)) {
 	if cp.kind == "row_query" {
 		if cp.before == "" && cp.after == "" && callbackName != "gorm:row_query" {
-			fmt.Printf("Registing RowQuery callback %v without specify order with Before(), After(), applying Before('gorm:row_query') by default for compatibility...\n", callbackName)
+			log.Printf("Registing RowQuery callback %v without specify order with Before(), After(), applying Before('gorm:row_query') by default for compatibility...\n", callbackName)
 			cp.before = "gorm:row_query"
 		}
 	}
@@ -109,7 +107,7 @@ func (cp *CallbackProcessor) Register(callbackName string, callback func(scope *
 // Remove a registered callback
 //     db.Callback().Create().Remove("gorm:update_time_stamp_when_create")
 func (cp *CallbackProcessor) Remove(callbackName string) {
-	fmt.Printf("[info] removing callback `%v` from %v\n", callbackName, fileWithLineNum())
+	log.Printf("[info] removing callback `%v` from %v\n", callbackName, fileWithLineNum())
 	cp.name = callbackName
 	cp.remove = true
 	cp.parent.processors = append(cp.parent.processors, cp)
@@ -122,7 +120,7 @@ func (cp *CallbackProcessor) Remove(callbackName string) {
 //		   scope.SetColumn("Updated", now)
 //     })
 func (cp *CallbackProcessor) Replace(callbackName string, callback func(scope *Scope)) {
-	fmt.Printf("[info] replacing callback `%v` from %v\n", callbackName, fileWithLineNum())
+	log.Printf("[info] replacing callback `%v` from %v\n", callbackName, fileWithLineNum())
 	cp.name = callbackName
 	cp.processor = &callback
 	cp.replace = true
@@ -161,7 +159,7 @@ func sortProcessors(cps []*CallbackProcessor) []*func(scope *Scope) {
 	for _, cp := range cps {
 		// show warning message the callback name already exists
 		if index := getRIndex(allNames, cp.name); index > -1 && !cp.replace && !cp.remove {
-			fmt.Printf("[warning] duplicated callback `%v` from %v\n", cp.name, fileWithLineNum())
+			log.Printf("[warning] duplicated callback `%v` from %v\n", cp.name, fileWithLineNum())
 		}
 		allNames = append(allNames, cp.name)
 	}