main_test.go

package main

import (
	"math/rand"
	"sort"
	"testing"
)

func BenchmarkInsertSorted(b *testing.B) {
	data := make([]int, b.N)
	for i := 0; i < b.N; i++ {
		data[i] = rand.Int()
	}

	a := []int{}

	for z := 0; z < len(data); z++ {
		x := data[z]

		i := sort.SearchInts(a, x)
		if i >= len(a) || a[i] != x {
			a = append(a, 0)
			copy(a[i+1:], a[i:])
			a[i] = x
		}
	}
}

func BenchmarkSortAfter(b *testing.B) {
	data := make([]int, b.N)
	for i := 0; i < b.N; i++ {
		data[i] = rand.Int()
	}

	a := []int{}

	for z := 0; z < len(data); z++ {
		x := data[z]
		a = append(a, x)
	}
	sort.Ints(a)
	j := 0
	for i := 1; i < len(a); i++ {
		if a[j] == a[i] {
			continue
		}
		j++
		a[j] = a[i]
	}
	a = a[:j+1]
}

Yup, don't do this. Leave the sorting to the last possible moment if you can. Maybe make a write-ahead-log or something.