defer vs no defer

bench_test.go

package main

import (
	"testing"
)

type conn struct{}

func (c *conn) Close() {}
func (c *conn) Value() bool {
	return true
}

var v bool

func benchmarkDefer() bool {
	conn := &conn{}
	defer conn.Close()
	return conn.Value()
}

func BenchmarkDefer(b *testing.B) {
	for n := 0; n < b.N; n++ {
		v = benchmarkDefer()
	}
}

func benchmarkNoDefer() bool {
	conn := &conn{}
	b := conn.Value()
	conn.Close()
	return b
}

func BenchmarkNoDefer(b *testing.B) {
	for n := 0; n < b.N; n++ {
		v = benchmarkNoDefer()
	}
}

output

# go test -v -bench=.
testing: warning: no tests to run
PASS
BenchmarkDefer		10000000	       110 ns/op
BenchmarkNoDefer	1000000000	       2.73 ns/op
ok  	tmp/apr	4.272s