bench_append.go

func Benchmark_append(b *testing.B) {
    b.StopTimer()

    b.ReportAllocs()
    b.StartTimer()

    for i := 0; i < 1000; i++ {
        var a []int
        for i := 0; i < 100000; i++ {
            a = append(a, i)
        }
    }
}

func Benchmark_noappend(b *testing.B) {
    b.StopTimer()

    b.ReportAllocs()
    b.StartTimer()

    for i := 0; i < 1000; i++ {
        var a = make([]int, 100000)
        for i := 0; i < 100000; i++ {
            a[i] = i
        }
    }
}

Results:

Benchmark_noappend-8          10000        113692 ns/op      802816 B/op           1 allocs/op
Benchmark_append-8           3000        469265 ns/op     4654338 B/op          30 allocs/op