Synchronize goroutines in your tests

I have been working on an emulator for the MOS 6502 Microprocessor, written in Go. As part of this package I have also implemented a minimal 6551 Asynchronous Communication Interface Adapter. The 6551 provides serial IO and is easy to use in combination with the 6502. When the microprocessor writes a byte to the 6551 it is stored in the tx (transmit) register where it’s available for other hardware components to read.