The documentation search on JuliaHub is pretty useful for this sort of thing, although info() is such a generic term that it’s hard to search for. The JuliaHub search does turn up the Logging.Logging module in its list, which is the correct answer.
The reason you can’t find info() as a package function is that it used to be a built-in function (in Julia 0.6 and earlier) and was replaced with the @info macro in Julia 0.7, 1.0, and all following versions. It’s possible that the example you’re following is pretty old (before summer of 2018), since it sounds like it’s using pre-1.0 Julia.
By the way, if you have other code that you want to run which was written pre-Julia 1.0, running it in Julia 0.7 can be very helpful. Julia 0.7 has the same functionality as Julia 1.0, but it also has helpful deprecation warnings for behaviors that were removed before 1.0. For example:
Julia 0.7:
julia> norm([1,2,3])
WARNING: Base.norm is deprecated: it has been moved to the standard library package `LinearAlgebra`.
Add `using LinearAlgebra` to your imports.
in module Main
3.7416573867739413
julia> info("hello world")
┌ Warning: `info()` is deprecated, use `@info` instead.
│ caller = top-level scope at none:0
└ @ Core none:0
INFO: hello world