What does 'incompatible' in go.mod mean, will it cause harm?

Question

I'm using goczmq in my project, something like next:

main.go:

package main

import (
    _ "github.com/zeromq/goczmq"
)

func main() {
}

And more, I'm using golang 1.12 with gomod to manage my project.

See next, I use go mod init xxx, and when build, it downloads goczmq automatically for me and add dependency to go.mod, but has incompatible in it. (But for other library I may get something like github.com/kolo/xmlrpc v0.0.0-20190717152603-07c4ee3fd181)

go.mod:

module pigeon

go 1.12

require (
    github.com/zeromq/goczmq v4.1.0+incompatible
)

From some discussion (for other library), e.g. this, it seems the library owner should do something to support golang 1.12? But in my case, all things works fine just a incompatible there make me a little worried (I mean all seems ok now, but some day when I use an api which I never used before, there will be hidden bomb there...?)

So my question:

Should I worry about this, or this is just as expected?

Answer 1

Accepted answer is correct, but really not friendly for me who just get in touch with go module. I made some investigation base on the answer & make a conclusion base on this as next, in case anyone needed:

Standard commands like go build or go test will automatically add new dependencies as needed to satisfy imports (updating go.mod and downloading the new dependencies). But there are several different situations which will result in the different version selections:

1. If a repository has not opted in to modules but has been tagged with valid semver tags, meanwhile, it's v0/v1 module, see this:

   not opted in to modules: means no go.mod in source tree

   valid semver tags: means the repo use git tag to tagged as something like vX.Y.Z

   v0/v1 module: means the value of major version(that is X) is 0 or 1, e.g. v0.1.0, v1.2.3

   Then, it will use a pseudo-version, something like github.com/kolo/xmlrpc v0.0.0-20190717152603-07c4ee3fd181

2. If a repository has not opted in to modules but has been tagged with valid semver tags, meanwhile, it's a v2+ module, see this:

   v2+ module: means the value of major version(that is X) is >=2,e g. v4.1.0

   Then, it will show as incompatible, something like github.com/zeromq/goczmq v4.1.0+incompatible

3. If a repository has already opted in to modules, but not have been tagged with valid semver tags:

   Then, it will behave as 1, use pseudo-version.

4. If a repository has already opted in to modules, and has been tagged with valid semver tags, meanwhile, it's a v0/v1 module:

   Then, it will behave normally like github.com/stretchr/testify v1.3.0

5. If a repository has already opted in to modules, and has been tagged with valid semver tags, meanwhile, it's a v2+ module:

   Then, when import in sourcecode, we need add /vN at the end, e.g., import "github.com/my/mod/v4", and in go.mod it will behave like github.com/my/mod/v4 v4.1.0