Cannot get latest version: module contains a go.mod file, so module path should be github.com/ipfans/echo-session/v4

[KateGo520]

Background

The github.com/Ipfans/echo-session uses Go modules and the current release version is v4. And it’s module path is "github.com/Ipfans/echo-session", instead of "github.com/Ipfans/echo-session/v4". It must comply with the specification of "Releasing Modules for v2 or higher" available in the Modules documentation. Quoting the specification:

A package that has opted in to modules must include the major version in the import path to import any v2+ modules
To preserve import compatibility, the go command requires that modules with major version v2 or later use a module path with that major version as the final element. For example, version v2.0.0 of example.com/m must instead use module path example.com/m/v2.
https://github.com/golang/go/wiki/Modules#releasing-modules-v2-or-higher

Steps to Reproduce

GO111MODULE=on, run go get targeting any version >= v4.0.0 of the Ipfans/echo-session:

$ go get github.com/ipfans/echo-session@v4.0.0
go: finding github.com/ipfans/echo-session v4.0.0
go: finding github.com/ipfans/echo-session v4.0.0
go get github.com/ipfans/echo-session@v4.0.0: github.com/ipfans/echo-session@v4.0.0: invalid version: module contains a go.mod file, so major version must be compatible: should be v0 or v1, not v4

Run go get github.com/Ipfans/echo-session, the version will stuck in v3.2.0:

$go get github.com/ipfans/echo-session
go: downloading github.com/ipfans/echo-session v3.2.0+incompatible
go: github.com/ipfans/echo-session upgrade => v3.2.0+incompatible

So anyone using Go modules will not be able to easily use any newer version of Ipfans/echo-session.

Solution

1. Kill the go.mod files, rolling back to GOPATH.

This would push them back to not being managed by Go modules (instead of incorrectly using Go modules).
Ensure compatibility for downstream module-aware projects and module-unaware projects projects

I see these dependencies in your go.mod file, which need modle awareness. So you'd better not use third-party tools(such as: Dep, glide, govendor…).

github.com/labstack/echo/v4 v4.1.6

You also need to update the import path to:

import github.com/labstack/echo/…

2. Fix module path to strictly follow SIV rules.

Patch the go.mod file to declare the module path as github.com/Ipfans/echo-session/v5 as per the specs. And adjust all internal imports.
The downstream projects might be negatively affected in their building if they are module-unaware (Go versions older than 1.9.7 and 1.10.3; Or use third-party dependency management tools, such as: Dep, glide,govendor…).

[*] You can see who will be affected here: [3 module-unaware user, i.e., Soontao/go-simple-api-gateway, xuybin/go-api-gateway, webinone/VCMS-GITHUB]
https://github.com/search?q=github.com%2Fipfans%2Fecho-session+filename%3Avendor.conf+filename%3Avendor.json+filename%3Aglide.toml+filename%3AGodep.toml&type=

If you don't want to break the above repos. This method can provides better backwards-compatibility.
Release a v2 or higher module through the major subdirectory strategy: Create a new v5 subdirectory (github.com/Ipfans/echo-session/v5) and place a new go.mod file in that subdirectory. The module path must end with /v5. Copy or move the code into the v5 subdirectory. Update import statements within the module to also use /v5 (import "github.com/Ipfans/echo-session/v5/…"). Tag the release with v5.x.y.

3. Suggest your downstream module users use hash instead of a version tag.

If the standard rule of go modules conflicts with your development mode. Or not intended to be used as a library and does not make any guarantees about the API. So you can’t comply with the specification of "Releasing Modules for v2 or higher" available in the Modules documentation.
Regardless, since it's against one of the design choices of Go, it'll be a bit of a hack. Instead of go get github.com/Ipfans/echo-session@version-tag, module users need to use this following way to get the Ipfans/echo-session:
(1) Search for the tag you want (in browser)
(2) Get the commit hash for the tag you want
(3) Run go get github.com/Ipfans/echo-session@commit-hash
(4) Edit the go.mod file to put a comment about which version you actually used
This will make it difficult for module users to get and upgrade Ipfans/echo-session.

[*] You can see who will be affected here: [13 module users, e.g., sasa-nori/nyaitter, elwin/heatmap, gotomsak/fe-learning-back]
https://github.com/search?l=&o=desc&q=github.com%2Fipfans%2Fecho-session+filename%3Ago.mod&s=indexed&type=Code

Summary

You can make a choice to fix DM issues by balancing your own development schedules/mode against the affects on the downstream projects.

For this issue, Solution 2 can maximize your benefits and with minimal impacts to your downstream projects the ecosystem.

References

• https://github.com/golang/go/wiki/Modules#semantic-import-versioning
• https://golang.org/cmd/go/#hdr-Module_compatibility_and_semantic_versioning
• https://github.com/golang/go/wiki/Modules#releasing-modules-v2-or-higher

[KateGo520]

@Atrox Could you help me review this issue? Thx :p

[ipfans]

Can you end a pull request for this issue?

[Atrox]

Hey @KateGo520, IMHO this is a non-issue. Many go libraries that migrated to go modules with a version greater than v1 have their go.mod without a version suffix. This makes the migration process for the library and dependent projects easier. If echo-session should reach v5 at some point then the go.mod should specify the /v5 suffix.

I don't see why you would try to install echo-session with the /v4 suffix when the README clearly states how you should go-get it (without the suffix).

I use echo-session without issues in all my projects (all on go modules). If you now decide that there should be an /v4 suffix, this is a breaking change and has to be done to a v5 which in turn means it is a /v5 suffix in the end.

I hope this clears up the reasoning behind the v4 currently having no /v4 suffix.

Thanks,
atrox

[KateGo520]

@Atrox Thanks for your reply. I get it.

[KateGo520]

@Atrox Follow the README direction, I run go get github.com/ipfans/echo-session. Then I found that I was stuck in v3.2.0. But the latest version is v4.0.0.

$go get github.com/ipfans/echo-session
go: downloading github.com/ipfans/echo-session v3.2.0+incompatible
go: github.com/ipfans/echo-session upgrade => v3.2.0+incompatible