How to check a channel is closed or not without reading it?

Question

This is a good example of workers & controller mode in Go written by @Jimt, in answer to \"Is there some elegant way to pause & resume any other goroutine in golang?

Answer 1

In a hacky way it can be done for channels which one attempts to write to by recovering the raised panic. But you cannot check if a read channel is closed without reading from it.

Either you will

• eventually read the "true" value from it (v <- c)
• read the "true" value and 'not closed' indicator (v, ok <- c)
• read a zero value and the 'closed' indicator (v, ok <- c)
• will block in the channel read forever (v <- c)

Only the last one technically doesn't read from the channel, but that's of little use.