Example from the docs:

    // pill.go
    package painkiller
    
    //go:generate stringer -type=Pill
    type Pill int

    const (
      Placebo Pill = iota
      Aspirin
      Ibuprofen
      Paracetamol
      Acetaminophen = Paracetamol
    )

Then running `go generate` will yield:

    $ cat pill_string.go
    // Code generated by "stringer -type=Pill"; DO NOT EDIT.
    
    package painkiller
    
    import "strconv"
    
    func _() {
     // An "invalid array index" compiler error signifies that the constant values have changed.
     // Re-run the stringer command to generate them again.
     var x [1]struct{}
     _ = x[Placebo-0]
     _ = x[Aspirin-1]
     _ = x[Ibuprofen-2]
     _ = x[Paracetamol-3]
    }
    
    const _Pill_name = "PlaceboAspirinIbuprofenParacetamol"
    
    var _Pill_index = [...]uint8{0, 7, 14, 23, 34}
    
    func (i Pill) String() string {
     if i < 0 || i >= Pill(len(_Pill_index)-1) {
      return "Pill(" + strconv.FormatInt(int64(i), 10) + ")"
     }
     return _Pill_name[_Pill_index[i]:_Pill_index[i+1]]
    }

Note: indentation is messing up because of Hacker News, so ignore the indentation.