func GetStackTracer(origErr error) StackTracer {
	var stacked StackTracer
	WalkDeep(origErr, func(err error) bool {
		if stackTracer, ok := err.(StackTracer); ok {
			stacked = stackTracer
			return true
		}
		return false
	})
	return stacked
}
GetStackTracer will return the first StackTracer in the causer chain.
This function is used by AddStack to avoid creating redundant stack traces.

You can also use the StackTracer interface on the returned error to get the stack trace.
package errors
import (
	"bytes"
	"fmt"
	"io"
	"path"
	"runtime"
	"strconv"
	"strings"
)
type StackTracer interface {
	StackTrace() StackTrace
}