▲ 5 ▼ Things that make Go channels expensive to implement

Recently, fchan: Fast Channels in Go made the rounds (via). I read it with some interest, because I'm always interested in interesting high-performance concurrent things like this, but my first reaction was that they'd started with an artificially inexpensive scenario. That got me thinking about what features make Go channels expensive (ie slower), regardless of the specifics of the implementation.