background worker while key-in

main.go

func until(cond func(), work func() bool) {
	endSig := make(chan struct{})
	go func() {
		for {
			select {
			case <-endSig:
				return
			default:
				if !work() {
					<-endSig
					return
				}
			}
		}
	}()
	cond()
	endSig <- struct{}{}
	close(endSig)
}

func mains() error {
  // :
		var ch string
		until(func() { ch, err = readline.GetKey(tty1) }, func() bool {
			if reader == nil {
				return false
			}
			row, err := uncsv.ReadLine(reader, mode)
			if err != nil {
				reader = nil
				if err != io.EOF {
					return false
				}
			}
			csvlines.PushBack(row)
			return err != io.EOF
		})
		if err != nil {
			return err
		}
  // :
}