asyncRead.swift

import Foundation
class ReadValue {
    var successClosure : ((String)->())? = nil
    var value : String = "" {
        didSet {
            if let closure = successClosure {
                closure(value)
            }
        }
    }
    func asyncRead( completed:@escaping (String)->() ) {
        successClosure = completed
        DispatchQueue.global().async {
            self.value = readLine() ?? ""
        }
    }
}
var read = ReadValue()
read.asyncRead { (readValue) in
    print(readValue)
    exit(1)
}

while(true) {
    
}