We loose the stack when the error is wrapped in cascade

package main

import (
	"fmt"

	"github.com/pkg/errors"
	"github.com/romanyx/stack"
)

func a() error {
	return errors.New("a")
}
func b() error {
	return stack.Errorf("b :%v", a())
}
func c() error {
	return stack.Errorf("c :%v", b())
}
func main() {
	err := c()
	for _, frame := range stack.Trace(err) {
		fmt.Printf("%s:%d %s()\n", frame.File, frame.Line, frame.Function)
	}
}

Result

/tmp/t/t.go:17 main.c()
/tmp/t/t.go:20 main.main()

With pkg/errors it's the opposite, the stack is three time. I would prefer to have full stack like that

/tmp/t/t.go:10 main.a()
/tmp/t/t.go:13 main.b()
/tmp/t/t.go:16 main.c()
/tmp/t/t.go:19 main.main()

Before:

BenchmarkErrorf/5-frames-4         	  158538	      7573 ns/op	    2992 B/op	      16 allocs/op
BenchmarkErrorf/10-frames-4        	   89179	     13124 ns/op	    4072 B/op	      26 allocs/op
BenchmarkErrorf/20-frames-4        	   44906	     26946 ns/op	    6232 B/op	      46 allocs/op
BenchmarkErrorf/40-frames-4        	   18634	     78400 ns/op	   13754 B/op	      87 allocs/op

After:

BenchmarkErrorf/5-frames-4         	  937490	      1248 ns/op	     384 B/op	       6 allocs/op
BenchmarkErrorf/10-frames-4        	  844726	      1510 ns/op	     384 B/op	       6 allocs/op
BenchmarkErrorf/20-frames-4        	  659119	      1842 ns/op	     384 B/op	       6 allocs/op
BenchmarkErrorf/40-frames-4        	  599695	      2035 ns/op	     384 B/op	       6 allocs/op