Make easier to test with time.Now as a config

[flibustenet]

Describe the feature

It's difficult to test function in main like now.BeginingOf... because it use time.Now()

I suggest that the function time.Now could be set global like
var WeekStartDay = time.Sunday

We could have
var TimeNowFunction = time.Now

now.BeginingOfDay() will become return With(TimeNowFunction()).BeginningOfDay()

Then when we start our test we just need to set
now.TimeNowFunction = func() time.Time { return time.Date(2021, 1, 1, 0, 0, 0, 0, time.Local) }

Thanks to listen

[Akaame]

It's difficult to test function in main like now.BeginingOf... because it use time.Now()

For testing purposes, one can just use the With free function which returns an instance of Now that has the same family of BeginningOf functions.

now.With(time.Date(2021, 1, 1, 0, 0, 0, 0, time.Local)).BeginningOfWeek()

Having said that, the ability the override such stuff exists in many Golang libraries via conventional OverrideFooFunc facilities, which seems like a good addition to this library but I do not see it bringing much of a value testing wise.

Cheers.

[flibustenet]

My purpose is to can test a function that use now.BeginingOf..., not to use now inside a test.
For example we cannot add a test in this package for the function now.BeginningOfWeek(). I mean it's an usual issue to test a function that use the current datetime...