concurrent map writes happened while use "options.WithGenerateUniqueValues(true)"

[Milk-Tang]

while I'm using faker.Username(options.WithGenerateUniqueValues(true)) in a concurrent scenario， "concurrent map writes" happened in the func generateUnique： https://github.com/go-faker/faker/blob/91fd09b0f81ca8520ead46dac24425c5db029861/faker.go#L1328-L1337