fix: unmarshal problem on env vars for type env string (#5037)

Signed-off-by: kevin <wanjunfeng@gmail.com>
Signed-off-by: Kevin Wan <wanjunfeng@gmail.com>

core/mapping/unmarshaler.go

@@ -30,9 +30,7 @@ var (
 	errValueNotSettable = errors.New("value is not settable")
 	errValueNotStruct   = errors.New("value type is not struct")
 	keyUnmarshaler      = NewUnmarshaler(defaultKeyName)
-	boolType            = reflect.TypeOf(false)
 	durationType        = reflect.TypeOf(time.Duration(0))
-	stringType          = reflect.TypeOf("")
 	cacheKeys           = make(map[string][]string)
 	cacheKeysLock       sync.Mutex
 	defaultCache        = make(map[string]any)
@@ -768,23 +766,25 @@ func (u *Unmarshaler) processFieldWithEnvValue(fieldType reflect.Type, value ref
 	}
 
 	derefType := Deref(fieldType)
-	switch derefType {
-	case boolType:
+	derefKind := derefType.Kind()
+	switch {
+	case derefKind == reflect.String:
+		SetValue(fieldType, value, toReflectValue(derefType, envVal))
+		return nil
+	case derefKind == reflect.Bool:
 		val, err := strconv.ParseBool(envVal)
 		if err != nil {
 			return fmt.Errorf("unmarshal field %q with environment variable, %w", fullName, err)
 		}
 
-		SetValue(fieldType, value, reflect.ValueOf(val))
+		SetValue(fieldType, value, toReflectValue(derefType, val))
 		return nil
-	case durationType:
+	case derefType == durationType:
+		// time.Duration is a special case, its derefKind is reflect.Int64.
 		if err := fillDurationValue(fieldType, value, envVal); err != nil {
 			return fmt.Errorf("unmarshal field %q with environment variable, %w", fullName, err)
 		}
 
-		return nil
-	case stringType:
-		SetValue(fieldType, value, reflect.ValueOf(envVal))
 		return nil
 	default:
 		return u.processFieldPrimitiveWithJSONNumber(fieldType, value, json.Number(envVal), opts, fullName)