lib/nat: Make service termination faster

[AudriusButkevicius]

Noticed it can take a while

[calmh]

Does util specifically use github.com/pkg/errors for wrapping? If so I guess this is fine (but should be flagged for future refactor), otherwise errors.Is seems more appropriate here now

[imsodin]

FYI: pkg/errors is compatible with go1.13's errors.Is/As methods.

[greatroar]

Actually, compatibility was withdrawn in pkg/errors 0.9.1.

package main

import (
	"fmt"
	"github.com/pkg/errors"
)

func main() {
	err := fmt.Errorf("wrapped: %w", fmt.Errorf("inner"))
	fmt.Println(errors.Cause(err)) // prints wrapped: inner
}

[imsodin]

Ok, not so nice - thanks for the hint. The other way around should still work as far as I see (i.e. you can use errors.Is on an error wrapped with errors.Wrap). So as we are using fmt.Errorf in places, we definitely shouldn't use errors.Cause anymore.

[AudriusButkevicius]

It's a wider fix that needs to happen through the codebase, hence I am still merging this.

Also, I am not sure this actually affects context.Cancelled, as it's created with errors.New so does not have Is, so the only way this could go wrong if something wrapped the error which then implemented Is and explicitly returned false.