bench.go

package main

import "testing"

var list []*struct{}

func init() {
	for i := 0; i < 1000; i++ {
		list = append(list, nil)
	}
}

func inPlace(input []*struct{}) []*struct{} {
	n := 0
	for _, i := range input {
		input[n] = i
		n++
	}
	return input[:n]
}

func newSlice(input []*struct{}) (output []*struct{}) {
	for _, i := range input {
		output = append(output, i)
	}
	return output
}

func Benchmark_Inplace(b *testing.B) {
	for n := 0; n < b.N; n++ {
		inPlace(list)
	}
}

func Benchmark_NewSlice(b *testing.B) {
	for n := 0; n < b.N; n++ {
		newSlice(list)
	}
}

bench.txt

Benchmark_Inplace-8    	 3655371	       325 ns/op	       0 B/op	       0 allocs/op
Benchmark_NewSlice-8   	  135073	      8602 ns/op	   16376 B/op	      11 allocs/op