UT failed in day_test.go

[slievrly]

• pkg/util/flagext/day_test.go fails in western timezones
  • Passes in China CST/UTC environments
    https://github.com/apache/incubator-seata-go/blob/master/pkg/util/flagext/day_test.go

[heliang666s]

please assign to me～

[slievrly]

@heliang666s already assigned to you.