diff --git a/copier.go b/copier.go
index 5fba6b8..05a5534 100644
--- a/copier.go
+++ b/copier.go
@@ -232,7 +232,8 @@ func copier(toValue interface{}, fromValue interface{}, opt Option) (err error)
 		}
 
 		// Get tag options
-		flgs, err := getFlags(dest, source, toType, fromType)
+		var flgs flags
+		flgs, err = getFlags(dest, source, toType, fromType)
 		if err != nil {
 			return err
 		}
@@ -247,7 +248,7 @@ func copier(toValue interface{}, fromValue interface{}, opt Option) (err error)
 				name := field.Name
 
 				// Get bit flags for field
-				fieldFlags, _ := flgs.BitFlags[name]
+				fieldFlags := flgs.BitFlags[name]
 
 				// Check if we should ignore copying
 				if (fieldFlags & tagIgnore) != 0 {
@@ -537,21 +538,17 @@ func lookupAndCopyWithConverter(to, from reflect.Value, converters map[converter
 
 	if cnv, ok := converters[pair]; ok {
 		result, err := cnv.Fn(from.Interface())
-
 		if err != nil {
 			return false, err
 		}
-
 		if result != nil {
 			to.Set(reflect.ValueOf(result))
 		} else {
 			// in case we've got a nil value to copy
 			to.Set(reflect.Zero(to.Type()))
 		}
-
 		return true, nil
 	}
-
 	return false, nil
 }
 
@@ -640,7 +637,7 @@ func checkBitFlags(flagsList map[string]uint8) (err error) {
 				err = fmt.Errorf("field %s has must tag but was not copied", name)
 				return
 			case flgs&(tagMust) != 0:
-				panic(fmt.Sprintf("Field %s has must tag but was not copied", name))
+				panic(fmt.Sprintf("field %s has must tag but was not copied", name))
 			}
 		}
 	}
@@ -682,7 +679,6 @@ func getFieldName(fieldName string, flgs flags) (srcFieldName string, destFieldN
 }
 
 func driverValuer(v reflect.Value) (i driver.Valuer, ok bool) {
-
 	if !v.CanAddr() {
 		i, ok = v.Interface().(driver.Valuer)
 		return
diff --git a/copier_tags_test.go b/copier_tags_test.go
index c8fe704..2c65ee8 100644
--- a/copier_tags_test.go
+++ b/copier_tags_test.go
@@ -49,6 +49,30 @@ func TestCopyTagMust(t *testing.T) {
 	copier.Copy(employee, user)
 }
 
+func TestCopyTagMustNoPanic(t *testing.T) {
+	type Student struct {
+		Name string
+	}
+	type Person struct {
+		Name  string
+		Grade string `copier:"must,nopanic"`
+	}
+
+	student := &Student{
+		Name: "jing1",
+	}
+	person := &Person{}
+	defer func() {
+		if r := recover(); r != nil {
+			t.Error("Expected no panic.")
+		}
+	}()
+	err := copier.Copy(person, student)
+	if err == nil {
+		t.Errorf("Expected err for not copy, got nil")
+	}
+}
+
 func TestCopyTagFieldName(t *testing.T) {
 	t.Run("another name field copy", func(t *testing.T) {
 		type SrcTags struct {
diff --git a/copier_test.go b/copier_test.go
index f6d68a4..2c0fdf5 100644
--- a/copier_test.go
+++ b/copier_test.go
@@ -1203,7 +1203,7 @@ func TestCopyMapOfInt(t *testing.T) {
 func TestCopyMapOfSliceValue(t *testing.T) {
 	// case1: map's value is a simple slice
 	key, value := 2, 3
-	src := map[int][]int{key: []int{value} }
+	src := map[int][]int{key: []int{value}}
 	dst1 := map[int][]int{}
 	var dst2 map[int][]int
 	err := copier.Copy(&dst1, src)
@@ -1240,10 +1240,10 @@ func TestCopyMapOfSliceValue(t *testing.T) {
 	// case2: map's value is a slice whose element is map
 	key1, key2 := 2, 3
 	value = 4
-	s := map[int][]map[int]int{key1: []map[int]int{ {key2: value} } }
-	d1 := map[int][]map[int]int{key1: []map[int]int{ {key1: key2 } } }
-	d2 := map[int][]map[int]int{key1: []map[int]int{ } }
-	d3 := map[int][]map[int]int{key1:  nil }
+	s := map[int][]map[int]int{key1: []map[int]int{{key2: value}}}
+	d1 := map[int][]map[int]int{key1: []map[int]int{{key1: key2}}}
+	d2 := map[int][]map[int]int{key1: []map[int]int{}}
+	d3 := map[int][]map[int]int{key1: nil}
 	d4 := map[int][]map[int]int{}
 	d5 := map[int][]map[int]int(nil)
 	ms := []map[int][]map[int]int{d1, d2, d3, d4, d5}
@@ -1267,7 +1267,7 @@ func TestCopyMapOfSliceValue(t *testing.T) {
 			for k, v := range m {
 				if k != key2 || v != value {
 					t.Errorf("Map's slice value should be copied recursively")
-				} 
+				}
 			}
 		}
 	}
@@ -1276,7 +1276,7 @@ func TestCopyMapOfSliceValue(t *testing.T) {
 func TestCopyMapOfPtrValue(t *testing.T) {
 	intV := 3
 	intv := intV
-	src := map[int]*int{2: &intv }
+	src := map[int]*int{2: &intv}
 	dst1 := map[int]*int{}
 	var dst2 map[int]*int
 	err := copier.Copy(&dst1, src)
@@ -1295,7 +1295,7 @@ func TestCopyMapOfPtrValue(t *testing.T) {
 		}
 
 		v3, ok := dst2[k]
-		if !ok || v3 == nil ||*v3 != *v1 || *v3 != intV {
+		if !ok || v3 == nil || *v3 != *v1 || *v3 != intV {
 			t.Errorf("Map should be copied")
 		}
 	}
@@ -1520,7 +1520,6 @@ func TestDeepCopyTime(t *testing.T) {
 	}
 }
 
-
 func TestNestedPrivateData(t *testing.T) {
 	type hasPrivate struct {
 		data int
@@ -1558,7 +1557,6 @@ func TestNestedPrivateData(t *testing.T) {
 	}
 }
 
-
 func TestDeepMapCopyTime(t *testing.T) {
 	t1 := time.Now()
 	t2 := t1.Add(time.Second)
@@ -1611,7 +1609,7 @@ func TestDeepCopySimpleTime(t *testing.T) {
 	}
 }
 
-type TimeWrapper struct{
+type TimeWrapper struct {
 	time.Time
 }