Since https://github.com/ooni/probe-cli/pull/527, if an experiment
returns an error, the corresponding measurement is not submitted since
the semantics of returning an error is that something fundamental
went wrong (e.g., we could not parse the input URL).
This diff ensures that all experiments only return and error when
something fundamental was wrong and return nil otherwise.
Reference issue: https://github.com/ooni/probe/issues/1808.
* fix(netxlite): make default resolver converge faster
Closes https://github.com/ooni/probe/issues/1726
* Update internal/netxlite/resolver.go
* fix(ndt7): adapt tests after previous change
Because now we're running the DNS resolution inside a goroutine
with a child context, the returned error string is different.
The previous error said we canceled the whole dialing operation,
while now we see directly that the context was canceled.
This is how I did it:
1. `git clone https://github.com/ooni/probe-engine internal/engine`
2. ```
(cd internal/engine && git describe --tags)
v0.23.0
```
3. `nvim go.mod` (merging `go.mod` with `internal/engine/go.mod`
4. `rm -rf internal/.git internal/engine/go.{mod,sum}`
5. `git add internal/engine`
6. `find . -type f -name \*.go -exec sed -i 's@/ooni/probe-engine@/ooni/probe-cli/v3/internal/engine@g' {} \;`
7. `go build ./...` (passes)
8. `go test -race ./...` (temporary failure on RiseupVPN)
9. `go mod tidy`
10. this commit message
Once this piece of work is done, we can build a new version of `ooniprobe` that
is using `internal/engine` directly. We need to do more work to ensure all the
other functionality in `probe-engine` (e.g. making mobile packages) are still WAI.
Part of https://github.com/ooni/probe/issues/1335
