Why the lenght of a channel without initialized capacity is 0?

gistfile1.txt

package main

import "fmt"
import "time"

func main() {

	c := make(chan int)
	go func() {
		for i := 0; i < 10; i += 1 {

			c <- i
			fmt.Println("sent:", i)
			time.Sleep(10 * time.Millisecond)
		}
	}()

	for {
		fmt.Println("len(c): ", len(c), cap(c))
		x := <-c
		time.Sleep(100 * time.Millisecond)
		fmt.Println("     got:", x)
		if x > 8 {
			break
		}
	}
	close(c)
}