[Question]: I know that is not possible to use more than 16 bit payload, but what's the reason?

[mirusky]

If there's no technical problem could make it configurable? Like:

// It will return a configurable instance.
instance := ksuid.NewInstance(ksuid.Config{
   MaxPayloadLength: 32,
})

And if possible a method to replace the global instance like golang zap:

instance := ksuid.NewInstance(ksuid.Config{
   MaxPayloadLength: 32,
})

// instance will create a 32 bit payload while ksuid.New() will create a 16 bit payload.
// to avoid that we could do something like:

undo := ksuid.ReplaceGlobals(instance)
defer undo()

// here the ksuid and instance are both configurable in the same way so I could call 
// ksuid.New() or instance.New() and both will create a 32 bit payload.