Merging Intervals out of hyphenated string ranges

I have a string like this:
ports := []string{"1", "2-7", "12-1200", "10-500"}

I would like to make an integer set out of this like the output should be :

[]intSet{ 1, 2-7, 10-1200 }

Where intSet is some kind of integer set from which I am able to easily remove and add elements.

Update 1

intSet is a list of sets.
So, 2-7 is also a set.

Update 2

Here the largest set is merged.

e.g.

• "1" -> 1
• "2-7" -> 2-7
• "12-1200" & "10-500" => "10..12.....500....1200" -> 10-1200

Since it's a set so it encompasses a unique range for this, a range which covers the whole set.

package main
import (
"fmt"
"log"
"strconv"
"strings"
)
type intSet struct {
start int
end   int
}
func (s intSet) String() string {
if s.start == s.end {
return fmt.Sprintf("%d", s.start)
}
return fmt.Sprintf("%d-%d", s.start, s.end)
}
func (s intSet) in(i int) bool {
return s.start <= i && i <= s.end
}
func (s *intSet) union(set intSet) {
if set.start < s.start {
s.start = set.start
}
if set.end > s.end {
s.end = set.end
}
}
func insert(set intSet, is []intSet) bool {
for i, s := range is {
if s.in(set.start) || s.in(set.end) {
is[i].union(set)
return true
}
//updated here with thankful to @mh-cbon
if set.in(s.start) || set.in(s.end) {
is[i].union(set)
return true
}
}
return false
}
func main() {
var set []intSet
ports := []string{"1", "2-7", "12-1200", "10-500", "9-5500"}
for _, port := range ports {
s := strings.Split(port, `-`)
if len(s) < 1 || len(s) > 2 {
log.Fatalln(`set cannot have multiple values or no value`)
}
start, err := strconv.Atoi(s[0])
if err != nil {
log.Fatalln(err)
}
end := start
if len(s) == 2 {
end, err = strconv.Atoi(s[1])
if err != nil {
log.Fatalln(err)
}
}
temSet := intSet{
start: start,
end:   end,
}
if !insert(temSet, set) {
set = append(set, temSet)
}
}
fmt.Println(set) //[1 2-7 9-5500]
}

run here