[Golang] make a slice and populate it by index or with `append`?

bm-slice.go

package main

import (
	"fmt"
	"testing"
)

func BenchmarkAppendFloat(b *testing.B) {
	benchmarks := []int{10, 100, 1000, 10000, 1e5}
	for _, bm := range benchmarks {
		b.Run(fmt.Sprintf("%d index", bm), func(b *testing.B) {
			for i := 0; i < b.N; i++ {
				s := make([]int, bm)
				for i := 0; i < bm; i++ {
					s[i] = i
				}
			}
		})
		b.Run(fmt.Sprintf("%d append", bm), func(b *testing.B) {
			for i := 0; i < b.N; i++ {
				s := make([]int, bm)
				for i := 0; i < bm; i++ {
					s = append(s, i)
				}
			}
		})
	}
}

//> go test -bench=.                                                                                           1
//BenchmarkAppendFloat/10_index-4         	30000000	        57.5 ns/op
//BenchmarkAppendFloat/10_append-4        	10000000	       166 ns/op
//BenchmarkAppendFloat/100_index-4        	 5000000	       334 ns/op
//BenchmarkAppendFloat/100_append-4       	 2000000	       892 ns/op
//BenchmarkAppendFloat/1000_index-4       	  500000	      2675 ns/op
//BenchmarkAppendFloat/1000_append-4      	  200000	      7280 ns/op
//BenchmarkAppendFloat/10000_index-4      	  100000	     21121 ns/op
//BenchmarkAppendFloat/10000_append-4     	   10000	    109381 ns/op
//BenchmarkAppendFloat/100000_index-4     	    5000	    203999 ns/op
//BenchmarkAppendFloat/100000_append-4    	    1000	   1456461 ns/op
//PASS