golang why don’t we have a set datastructure [closed]

One reason is that it is easy to create a set from map:

s := map[int]bool{5: true, 2: true}
_, ok := s[6] // check for existence
s[8] = true // add element 
delete(s, 2) // remove element

Union

s_union := map[int]bool{}
for k, _ := range s1{
    s_union[k] = true
}
for k, _ := range s2{
    s_union[k] = true
}

Intersection

s_intersection := map[int]bool{}
if len(s1) > len(s2) {
  s1, s2 = s2, s1 // better to iterate over a shorter set
}
for k,_ := range s1 { 
  if s2[k] {
    s_intersection[k] = true
  }
}

It is not really that hard to implement all other set operations.