The Go modules wiki page is over 60 pages long so there is quite a bit of a learning curve to get it right the first time. When releasing the v2 version of the NATS server earlier this year, we adopted modules, renamed our repos, bump the major version of the project (including client libraries too) all at the same time. In this talk, one of the NATS maintainers will give a quick overview of everything that was impacted from the changes and how all problems were eventually solved.

1. Adopting Go modules in NATS v2
Gopherpalooza / November 2019
Waldemar Quevedo / @wallyqs
💦
🔥

2. @wallyqs
#Gopherpalooza
Heads up: A few Game Of Thrones
spoilers in this talk… 👀

3. @wallyqs
#Gopherpalooza
● Waldemar Quevedo / @wallyqs
● Software Engineer at Synadia Communications, Inc
● NATS core maintainer (Ruby, Python, Go, K8S)
● Author of Practical NATS (Apress, 2018)
About me

4. @wallyqs
#Gopherpalooza
What is NATS?

5. @wallyqs
#Gopherpalooza
NATS is a simple,
production proven,
cloud-native
messaging system.

6. @wallyqs
#Gopherpalooza
NATS Intro
● Created by Derek Collison in 2010 for CloudFoundry
● DNA: Simplicity, performance, security, and availability
● TCP/IP based with a very simple plain text protocol
| PUB | SUB | UNSUB | CONNECT | INFO | MSG | -ERR | +OK | PING | PONG |

7. @wallyqs
#Gopherpalooza
Next year: #NATSTurns10

8. @wallyqs
#Gopherpalooza
CNCF Landscape
Joined CNCF as an
incubation project
in 2018
https://landscape.cncf.io

9. @wallyqs
#Gopherpalooza
CNCF Landscape
Joined CNCF as an
incubation project
in 2018
https://landscape.cncf.io

10. @wallyqs
#Gopherpalooza
CNCF Landscape

11. @wallyqs
#Gopherpalooza
In May 2019, the NATS team was
ready to ship the biggest release
of the server so far...

12. @wallyqs
#Gopherpalooza
NATS v2 spike
A lot of development happened in 2018

13. @wallyqs
#Gopherpalooza
Meanwhile...

14. @wallyqs
#Gopherpalooza
Modules made it into Go 1.11
● Solution for dependencies so far used by NATS projects
was vendoring with `gvt` but got retired
● Team was still on the fence of whether to use `dep`

15. @wallyqs
#Gopherpalooza
dep?
I am not sure what you are now

16. @wallyqs
#Gopherpalooza
dep?
That’s not important

17. @wallyqs
#Gopherpalooza
OK, using Go Modules 😬

18. @wallyqs
#Gopherpalooza
Original plan for NATS v2 release
● Adopt Go Modules to get a reproducible build
● Rename the server repos:
○ From: github.com/nats-io/gnatsd
○ To: github.com/nats-io/nats-server
● Rename the client repos:
○ From: github.com/nats-io/go-nats
○ To: github.com/nats-io/nats.go
● Bump client and server version to v2 (git tag)

19. @wallyqs
#Gopherpalooza
Adopting Go modules
⚠
● Simple enough

20. @wallyqs
#Gopherpalooza
Original plan for NATS v2 release
● Adopt Go Modules to get a reproducible build
● Rename the server repos:
○ From: github.com/nats-io/gnatsd
○ To: github.com/nats-io/nats-server
● Rename the client repos:
○ From: github.com/nats-io/go-nats
○ To: github.com/nats-io/nats.go
● Bump client and server version to v2 (git tag)
✅

21. @wallyqs
#Gopherpalooza
NATS repo has changed often
● Past names of NATS repo:
github.com/apcera/nats
github.com/nats-io/nats
github.com/nats-io/go-nats
github.com/nats-io/nats.go (← current)

22. @wallyqs
#Gopherpalooza
Original plan for NATS v2 release
● Adopt Go Modules to get a reproducible build
● Rename the server repos:
○ From: github.com/nats-io/gnatsd
○ To: github.com/nats-io/nats-server
● Rename the client repos:
○ From: github.com/nats-io/go-nats
○ To: github.com/nats-io/nats.go
● Bump client and server version to v2 (git tag)
✅
✅

23. @wallyqs
#Gopherpalooza
Here be dragons… 🐉

24. @wallyqs
#Gopherpalooza
🔥🔥🔥
Lots of broken projects!!!
“No such file?”
Same dependency twice
using different names??

25. @wallyqs
#Gopherpalooza
Time to rollback (what we can…)

26. @wallyqs
#Gopherpalooza
Only v2 tag in the server
● Changing both client and server to v2 series turned out too
big of a change for the ecosystem 🤯
Missed this!

27. @wallyqs
#Gopherpalooza
Couldn’t rollback name change
● Already out there so created read-only versions of the old
name pre modules

28. @wallyqs
#Gopherpalooza
`go get` fetching v1 by default

29. @wallyqs
#Gopherpalooza
More `go get` issues

30. @wallyqs
#Gopherpalooza
`go get` issues with dots in names
https://github.com/golang/go/issues/32483

31. @wallyqs
#Gopherpalooza
Got worse in Go 1.13
https://github.com/golang/go/issues/32483

32. @wallyqs
#Gopherpalooza
Fixed in Go1.13.3 by @jayconrod
https://github.com/golang/go/issues/32483

33. @wallyqs
#Gopherpalooza
Dot in names now ok to use
Trailing slash
workaround also
supported for
now

34. @wallyqs
#Gopherpalooza
What we should have done...

35. @wallyqs
#Gopherpalooza
What we should have done
● Carefully read the wiki entry about modules (60 pages!)
https://github.com/golang/go/wiki/Modules
● Thankfully more guides are appearing now:
https://blog.golang.org/v2-go-modules

36. @wallyqs
#Gopherpalooza
What we should have done
● Renaming a Go project is extremely difficult
https://github.com/golang/go/wiki/Resolving-Problems-
From-Modified-Module-Path

37. @wallyqs
#Gopherpalooza
What we should have done
● Before adopting modules, definitely join #modules
channel in Gophers slack and look at recent issues

38. @wallyqs
#Gopherpalooza
What we should have done
● Make a careful plan, Kubernetes good example:
https://github.com/kubernetes/enhancements/blob/master/keps/sig-arch
itecture/2019-03-19-go-modules.md

39. @wallyqs
#Gopherpalooza
Questions?

40. @wallyqs
#Gopherpalooza
https://natsio.slack.com
Ping us in Slack if have issues with NATS
and/or Go modules 🙏