Q: What’s the difference between buffered and unbuffered channels?

main.go

package main

import (
	"fmt"
	"time"
)

func main() {
	unbuf := make(chan int)          // 0-capacity ➜ send blocks until a receiver is ready
	buf   := make(chan int, 2)       // capacity = 2

	go func() {                      // receiver
		fmt.Println(<-unbuf)         // ← blocks until sender arrives
		for v := range buf {         // drains buffered chan
			fmt.Println(v)
		}
	}()

	unbuf <- 1                       // blocks → receiver unblocks, prints 1

	buf <- 10                        // enqueued (no block)
	buf <- 20                        // enqueued (no block, buffer full now)
	// buf <- 30  // would block – buffer is full

	close(buf)
	time.Sleep(200 * time.Millisecond)
}