buffered/unbuffered channel impl.

channel.go

package main

import (
	"fmt"
	"time"
)

func main() {
	c := make(chan int) // Allocate a channel.
	// uncomment this line
	// c := make(chan int, 1) // Allocate a channel.
	// Start the sort in a goroutine; when it completes, signal on the channel.
	go func() {
		time.Sleep(time.Second * 1)

		// sort.Sort()
		c <- 1 // Send a signal; value does not matter.
		fmt.Println("c <- 1")
		time.Sleep(time.Second * 2)

	}()
	time.Sleep(time.Second * 10)
	// doSomethingForAWhile()
	<-c // Wait for sort to finish; discard sent value.
	fmt.Println("<-c")
	time.Sleep(time.Second * 2)
}

Receivers always block until there is data to receive. If the channel is unbuffered, the sender blocks until the receiver has received the value. If the channel has a buffer, the sender blocks only until the value has been copied to the buffer; if the buffer is full, this means waiting until some receiver has retrieved a value.