Golang benchmark check buffered channel has ready-to-read value

gistfile1.txt

# go test -bench=.
goos: linux
goarch: amd64
pkg: tmp/eh4
BenchmarkSelect-8   	200000000	         7.65 ns/op
BenchmarkLen-8      	2000000000	         1.07 ns/op
PASS
ok  	tmp/eh4	4.580s

main_test.go

package main

import (
	"fmt"
	"testing"
	"time"
)

var chn = make(chan int, 1000)

func init() {
	go func() {
		time.Sleep(time.Hour)
		chn <- 0
	}()
}

func BenchmarkSelect(b *testing.B) {
	for n := 0; n < b.N; n++ {
		select {
		case v := <-chn:
			fmt.Printf("have value\n", v)
		default:
		}
	}
}

func BenchmarkLen(b *testing.B) {
	for n := 0; n < b.N; n++ {
		if len(chn) != 0 {
			v := <-chn
			fmt.Printf("have value: %v\n", v)
		}
	}
}