Goのclosureへのパラメータの渡し方

closure.go

package closure

type Request struct {
	Url string
}

func Closure1(reqs []*Request) {
	for _, req := range reqs {
		go func(req *Request) {
			req.Url = "http://example.org"
		}(req)
	}
}

func Closure2(reqs []*Request) {
	for _, req := range reqs {
		req := req
		go func() {
			req.Url = "http://example.org"
		}()
	}
}

closure_test.go

package closure

import (
	"testing"
)

func testHelper() []*Request {
	reqs := make([]*Request, 10000)
	for i := 0; i < len(reqs); i++ {
		reqs[i] = &Request{}
	}
	return reqs
}

func BenchmarkClosure1(b *testing.B) {
	reqs := testHelper()
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		Closure1(reqs)
	}
}

func BenchmarkClosure2(b *testing.B) {
	reqs := testHelper()
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		Closure2(reqs)
	}
}

results

BenchmarkClosure1        500       5356625 ns/op       11165 B/op         38 allocs/op
BenchmarkClosure2        500       6917004 ns/op      262473 B/op      20029 allocs/op