Example test

main_test.go

package main

import (
        "sync"
        "testing"
)

func TestAppend(t *testing.T) {
        x := []string{"start"}

        wg := sync.WaitGroup{}
        wg.Add(2)
        go func() {
                defer wg.Done()
                y := append(x, "hello", "world")
                t.Log(cap(y), len(y))
        }()
        go func() {
                defer wg.Done()
                z := append(x, "goodbye", "bob")
                t.Log(cap(z), len(z))
        }()
        wg.Wait()
}