Merging two sorted slices

It is necessary to implement the function mergeSorted(a, b []int) []int, which:

• takes two slices of integers, already sorted in ascending order;
• forms and returns a new slice containing elements of both input slices in a single ascending order.

import "fmt"

func main() {
    var first = []int{1, 5, 6, 18, 99}
    var second = []int{2, 4, 9, 11}
    fmt.Println(mergeSorted(first, second))
}

func mergeSorted(first []int, second []int) []int {
    // implementation of the task
}