How Channel Internals Work in Go (hchan Struct)

Go channels are implemented internally as the hchan struct in src/runtime/chan.go, which manages a circular buffer, send/receive queues, and a mutex lock.

type hchan struct {
	qcount   uint           // total data in the queue
	dataqsiz uint           // size of the circular queue
	buf      unsafe.Pointer // points to an array of dataqsiz elements
	elemsize uint16
	closed   uint32
	timer    *timer
	elemtype *_type
	sendx    uint
	recvx    uint
	recvq    waitq // list of recv waiters
	sendq    waitq // list of send waiters
	lock     mutex
}

The hchan struct is the internal blueprint for every channel in Go, acting like a secure pipe with a waiting room. It holds the actual data buffer, tracks how full the pipe is, and maintains two separate lines of waiting goroutines for senders and receivers. A built-in lock ensures that only one goroutine can modify the channel's state at a time to prevent data corruption.