Package cryptorand implements a mockable source or crypto strong randomness.
In real world scenario it is same source as provided by crypt/rand. In tests it is replaced with reproducible, not really random stream of bytes.
Get returns an io.Reader that emits random stream of bytes.
Usually this returns crypto/rand.Reader, but unit tests may replace it with a mock by using 'MockForTest' function.
MockForTest installs deterministic source of 'randomness' in the context.
Must not be used outside of tests.
Read is a helper that reads bytes from random source using io.ReadFull.
On return, n == len(b) if and only if err == nil.