v1.4.0

• Deprecate the package variable PRNG used in ExpJitterDelay as it was not safe for concurrent use by default, ExpJitterDelay will now use the stdlib rand.Int63n function which is concurrency-safe.
• Introduce the new ExpJitterDelayWithRand that is the same as ExpJitterDelay except that it accepts a function to generate the random number. It is the caller's responsibility to ensure that this function is safe for concurrent use.

Thanks to @justinrixx for raising the issue and contributing the fix.