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The non-blocking read parts is also easy, but that's also only one use-case for Go's select. The harder part is the generic "wait until one of the select cases can be taken".

You can't implement this with non-blocking reads alone. If you would, it would be something like busy spinning and iterating through all select cases and trying none-blocking reads until one succeeds. But that's just not efficient.

You need a mechanism instead which also registers a pending select at each event source and unregisters it when done. And the event source (e.g. channel) must wake up one or more select when it's state changes.




Adding a condition-variable per select and keeping a list of pointers in each channel that are pinged when data arrives is the easiest approach I can think of. Haven't tried that one though, I have honestly never run into a use case where I needed select for channels outside of Go.




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