fix: Fix bug of missing timezone in TestNow settings

Author: kuafuRace

traveler.go

@@ -7,9 +7,6 @@ import (
 // Now returns a Carbon instance for now.
 // 当前
 func Now(timezone ...string) *Carbon {
-	if IsTestNow() {
-		return frozenNow.testNow.Copy()
-	}
 	var (
 		tz  string
 		loc *Location
@@ -20,6 +17,9 @@ func Now(timezone ...string) *Carbon {
 	} else {
 		tz = DefaultTimezone
 	}
+	if IsTestNow() {
+		return frozenNow.testNow.Copy().SetTimezone(tz)
+	}
 	if loc, err = parseTimezone(tz); err != nil {
 		return &Carbon{Error: err}
 	}

traveler_example_test.go

@@ -11,32 +11,38 @@ func ExampleNow() {
 
 	carbon.SetTestNow(carbon.Parse("2020-08-05"))
 
-	fmt.Println(carbon.Now(carbon.UTC).ToString())
+	fmt.Println(carbon.Now().ToString())
+	fmt.Println(carbon.Now(carbon.PRC).ToString())
 
 	// Output:
 	// 2020-08-05 00:00:00 +0000 UTC
+	// 2020-08-05 08:00:00 +0800 CST
 }
 
 func ExampleTomorrow() {
 	defer carbon.CleanTestNow()
 
 	carbon.SetTestNow(carbon.Parse("2020-08-05"))
 
-	fmt.Println(carbon.Tomorrow(carbon.UTC).ToString())
+	fmt.Println(carbon.Tomorrow().ToString())
+	fmt.Println(carbon.Tomorrow(carbon.PRC).ToString())
 
 	// Output:
 	// 2020-08-06 00:00:00 +0000 UTC
+	// 2020-08-06 08:00:00 +0800 CST
 }
 
 func ExampleYesterday() {
 	defer carbon.CleanTestNow()
 
 	carbon.SetTestNow(carbon.Parse("2020-08-05"))
 
-	fmt.Println(carbon.Yesterday(carbon.UTC).ToString())
+	fmt.Println(carbon.Yesterday().ToString())
+	fmt.Println(carbon.Yesterday(carbon.PRC).ToString())
 
 	// Output:
 	// 2020-08-04 00:00:00 +0000 UTC
+	// 2020-08-04 08:00:00 +0800 CST
 }
 
 func ExampleCarbon_AddDuration() {