The short answer: you can't, and it is a feature.
The runtime "injects" certain functions into certain packages in order to
build a bridge between the (internal) runtime and the "package world"
accessible to programmers. Thus, they are only accessible in that package
specific package (time).
The reason for this choice is encapsulation. By not exposing a given
function, the Go authors and developers are free to change the internal
runtime interface, as long as they still provide the exported function
Now(). If you were to get access to it, the Go 1.0 backwards compatibility
guarantee would easily be broken for your program, since it is likely it
will change in the future. Furthermore, any exposed function requires
documentation. Some times you hide details from the outside world because
the documentation effort is simply too large in the first place.
The solution Go uses is fairly standard in language runtimes. You do not
want to expose all of the runtime to the user. The reason is that this
removes every notch of flexibility you have as a runtime developer, because
most changes are going to break someones program in some way. As an aside,
languages such as Ruby or Python are now very hard to optimize for, because
they have exposed a vast set of internals to the outside world. This "locks
them down" so to speak.
If you do need more specific access, there is usually an underlying idea
you have in mind. It would probably be better to discuss why you need the
access in the first place. It might be useful to other people. The new use
could be an extension to the current interface such that you still have the
necessary compatiblity. It is, perhaps, also worth looking at for a Go 2.x.
On Sun, Oct 15, 2017 at 2:59 AM traetox <trae...@gmail.com> wrote:
> I would like to be able to call the runtime implemented "now()" function
> similar to how the "time" package does.
>
> For example the Time.Now() function in the time package looks like the
> following
>
> func now() (sec int64,nsec int32, mono int64)
> func Now() Time{
> sec, nsec, mono := now()
> ...
> }
>
>
> When I build packages using "go build" using the same structure I get the
> error:
> missing function body for "now"
>
> How is this package built such that it can access the "now()" function and
> how can I access those runtime implemented functions in my own packages?
>
> Thank you!
>
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