Goroutines vs Threads

Goroutines are lightweight, user-space threads managed by the Go runtime, while threads are heavier, OS-managed execution units. Goroutines are more efficient because the Go runtime multiplexes thousands of them onto a smaller number of OS threads, whereas threads are created and scheduled directly by the operating system.

// Goroutine: Lightweight, managed by Go runtime
func worker() { /* ... */ }

// Start a goroutine (costs ~2KB stack initially)
go worker()

// Thread: Heavyweight, managed by OS (via cgo/pthreads)
// Requires explicit binding to an OS thread
runtime.LockOSThread()
// Now this goroutine runs on a dedicated OS thread

Think of goroutines as tiny, cheap tasks that the Go program manages itself, allowing you to run thousands at once without slowing down. Threads are like full-time employees hired by the operating system; they are powerful but expensive to create and manage. You use goroutines for almost everything in Go to handle many tasks simultaneously, while you only use threads when you need to interact directly with the operating system or external C libraries.