errors.go

package main

import (
    "fmt"
    "strings"
    "time"
)

type withMessage struct {
    msg   string
    cause *withMessage
}

func (w *withMessage) Quadratic() string {
    if w == nil {
        return ""
    }
    return w.msg + ": " + w.cause.Quadratic()
}

func (w *withMessage) Linear() string {
    chain := []string{w.msg}
    wc := w
    for wc != nil {
        chain = append(chain, wc.msg)
        wc = wc.cause
    }
    return strings.Join(chain, ": ")
}

func main() {
    wc := &withMessage{"msg", nil}
    pos := wc
    for i := 0; i < 20000; i++ {
        pos = &withMessage{"msg", pos}
    }
    now := time.Now()
    l := len(pos.Quadratic())
    fmt.Println("quadratic", time.Since(now), l)

    now = time.Now()
    l = len(pos.Linear())
    fmt.Println("linear", time.Since(now), l)
}