How Go select Works Internally

Concurrency

2026-04-17T12:05:42+00:00

Go's select statement blocks until one channel operation is ready, then executes that single operation pseudo-randomly if multiple are available.

Go's select statement works by blocking until one or more of its channel operations can proceed, then executing exactly one chosen operation in a pseudo-random order if multiple are ready. It does not execute all ready cases simultaneously; it picks one and ignores the rest for that cycle.

select {
    case msg := <-ch1:
        fmt.Println("Received from ch1:", msg)
    case ch2 <- "hello":
        fmt.Println("Sent to ch2")
    default:
        fmt.Println("No channels ready")
}