How Go Channels Coordinate Goroutines

Channels let goroutines exchange typed values and synchronize their work. Create one with make(chan T), send with ch <- v, and receive with <-ch. When an operation cannot proceed, it blocks the goroutine performing it, not every goroutine in the program.

An unbuffered send can proceed only when a receiver is ready, so the handoff synchronizes the two goroutines. A buffered channel can hold up to its fixed capacity. Sends proceed while space remains and block when the buffer is full. Receives from an open channel block when the buffer is empty. This bounded buffer can provide backpressure, but it is not an unbounded message queue. A select considers several channel operations and chooses one that can proceed.

Closing a channel records that no more values will be sent; it is not required for garbage collection. Receivers first drain any buffered values. After that, receives return the element type's zero value immediately, with ok == false in v, ok := <-ch. Sending to a closed channel panics. Sending or receiving on a nil channel blocks forever. A nil channel can disable a select case, but using one accidentally can cause a deadlock.