how to create a serial queue in swift4 [duplicate]

问题

This question already has answers here:

How to create dispatch queue in Swift 3 (15 answers)

Type 'DispatchQueue.Attributes' has no member 'serial' (1 answer)

Closed last year.

DispatchQueue.init(label: , qos:  , attributes: , autoreleaseFrequency:  , target:  )

How to write the parameters, I looked at the original notes for a long time，But I still can't write a serial queue

来源：https://stackoverflow.com/questions/50129528/how-to-create-a-serial-queue-in-swift4