Go Modules: finding out right pseudo-version (vX.Y.Z-<timestamp>-<commit>) of required package
Solution 1
A version of the form v0.0.0-20180906233101-161cd47e91fd
means that there are no tagged versions on the git repository. So go mod
generates one based on the latest commit time and the prefix of the commit hash.
To get a correct go.mod
file start out using the following command (assuming go 1.11):
go mod init yourmodulename
Or create an empty go.mod file that just contains the following:
module yourmodulename
then run go mod tidy
, this will find all dependencies, add the missing and remove the unused dependencies.
Solution 2
Update
This command is the better solution to adding the replace
command to go.mod
rather than doing it manually using git
that I initially posted:
go mod edit -replace github.com/docker/docker=github.com/docker/engine@ea84732a7725
produces a similar result but instead of using a pseudo-version, it finds the tagged engine version.
replace github.com/docker/docker => github.com/docker/engine v17.12.0-ce-rc1.0.20191113042239-ea84732a7725+incompatible
Alternatively, include a tagged docker version.
go mod edit -replace github.com/docker/[email protected]=github.com/docker/engine@ea84732a7725
for
replace github.com/docker/docker v1.13.1 => github.com/docker/engine v17.12.0-ce-rc1.0.20191113042239-ea84732a7725+incompatible
Thanks to @Shivam010 on Medium
Original, deprecated answer
Here's how I did it.
Checkout the repository on the desired branch/tag. e.g.
git clone -b v19.03.5 [email protected]:docker/engine.git
Then
cd engine
TZ=UTC git --no-pager show \
--quiet \
--abbrev=12 \
--date='format-local:%Y%m%d%H%M%S' \
--format="%cd-%h"
And i get
20191113042239-ea84732a7725
For use in go.mod
as
replace github.com/docker/docker v1.13.1 => github.com/docker/engine v0.0.0-20191113042239-ea84732a7725
Solution 3
The author is using version strings like v0.0.0-20170922011244-0744d001aa84, consisting of the semver indication v0.0.0, a timestamp and something that looks like a git commit ID.
How do I figure out those version strings?
You never need to manually figure out those complex version strings, which are called pseudo-versions.
Daily workflow
Your typical daily workflow can be:
- Add import statements to your
.go
code as needed. - Standard commands like
go build
,go test
, orgo mod tidy
will automatically add new dependencies as needed to satisfy imports (updatinggo.mod
and downloading the new dependencies). By default, the@latest
version of a new direct dependency will be used. - When needed, more specific versions of dependencies can be chosen with commands such as:
go get [email protected]
go get foo@e3702bed2
go get foo@latest
go get foo@branch
- or by editing
go.mod
directly.
Note that you did not need to come up with a pseudo-version on your own in any of those examples, even when requesting a specific commit (e.g., @e3702bed2
), or the latest commit on a branch (e.g., @master
).
When do I see pseudo-versions in my go.mod
?
If you end up with a version that resolves to a valid semver tag with a leading v
such as v1.2.3
or v1.2.4-beta-1
, then that semver tag will be recorded in your go.mod
file. If the version does not have a valid semver tag, then it will be instead recorded with as a pseudo-version in your go.mod
file, such as v0.0.0-20171006230638-a6e239ea1c69
, which includes a version section, a commit timestamp, and a commit hash.
In your particular case, golang.org/x/net/html
does not have any semver tags, which means if you do go get golang.org/x/net/html@latest
, or go get golang.org/x/net/html@0744d001aa84
, or just do go build
after first including import "golang.org/x/net/html"
in your .go
file, then golang.org/x/net/html will be recorded in your go.mod
as a pseudo-version, but note that you did not need to figure out the complex string yourself (because the go
command translates modules queries such as go get golang.org/x/net/html@0744d001aa84
into the corresponding pseudo-version when needed, and records the result in your go.mod
).
Why was the pseudo-version format chosen?
The pseudo-version format helps provide a simple total ordering across all versions based on standard semver ordering, which makes it easier to reason about what commit will be considered "later" than another commit, or whether an actual semver tag is considered "later" than a separate commit.
Controlling dependency versions
You can read more about all of the above in the "How to Upgrade and Downgrade Dependencies" section of the Go Modules wiki, which also contains additional links into the official documentation.
Solution 4
Now I read a bit further in the documentation (go help modules
) and stumbled upon go mod tidy
:
The 'go mod tidy' command builds that view and then adds any missing module requirements and removes unnecessary ones.
So when I leave away the requirement on golang.org/x/net/html
and prune my go.mod
file to this:
module github.com/patrickbucher/prettyprint
And then run go mod tidy
, then the requirement with the version number is correctly figured out based on the import path in my source code, and thus go.mod
becoming:
module github.com/patrickbucher/prettyprint
require golang.org/x/net v0.0.0-20180906233101-161cd47e91fd
Now both go list
and go build
work.
Solution 5
If you want to use a specific commit which has not yet been tagged, you could do the following -
module github.com/patrickbucher/prettyprint
require golang.org/x/net 73496e0df0ba4284f460d1955ddf6bb096957c9f
then run go mod tidy
and you will automatically see the pseudo-version in the go.mod file, becoming
module github.com/patrickbucher/prettyprint
require golang.org/x/net v0.0.0-20180906233101-161cd47e91fd
(I borrowed the code snippet from Patrick's response above)
Patrick Bucher
I'm Patrick from Switzerland. I did an apprenticeship in IT and then worked for a couple of years as a Java Programmer and Web Engineer (using Java, JSP, JavaScript, HTML, SQL, CSS, bash, Debian Linux). Besides working as a backend developer at PEAX, I'm studying computer science. I'm also interested in Linux (Debian, Arch), Python, Go, R and C. When I am not sitting at the keyboard, I read a lot, learn languages (English, Russian, French) or take long walks in the woods. I consider myself a minimalist, both in my life style and as a programmer.
Updated on June 24, 2021Comments
-
Patrick Bucher almost 3 years
I am trying out Go modules. My project requires the libarary
golang.org/x/net/html
, so I defined thisgo.mod
file:module github.com/patrickbucher/prettyprint require golang.org/x/net/html
And wrote this demo program to check if the dependency gets loaded upon compilation:
package main import ( "fmt" "log" "os" "golang.org/x/net/html" ) func main() { doc, err := html.Parse(os.Stdin) if err != nil { log.Fatal(err) } fmt.Println(doc) }
When I run go build, I get this error message:
go: errors parsing go.mod: ~/prettyprint/go.mod:3: usage: require module/path v1.2.3
Obviously, I missed the version number. But which one to take? I stumbled an article called Takig Go Modules for a Spin, where I found an example of a
go.mod
file containing references togolang.org/x
packages:module github.com/davecheney/httpstat require ( github.com/fatih/color v1.5.0 github.com/mattn/go-colorable v0.0.9 github.com/mattn/go-isatty v0.0.3 golang.org/x/net v0.0.0-20170922011244-0744d001aa84 golang.org/x/sys v0.0.0-20170922123423-429f518978ab golang.org/x/text v0.0.0-20170915090833-1cbadb444a80 )
The author is using version strings like
v0.0.0-20170922011244-0744d001aa84
, consisting of the semver indication v0.0.0, a timestamp and something that looks like a git commit ID.How do I figure out those version strings? I guess those
golang.org/x
packages will be versioned according to semantic versioning at some point, but to really trying outgo mod
, I need to figure out those now. -
thepudds almost 5 yearsMinor side note: you don't necessarily need to run
go mod tidy
to have thego
command automatically determine the corresponding pseudo-version in this case. Other commands likego build
,go test
, etc. would also have recorded the version. Some more details in this answer.go mod tidy
has its uses, but sometimes people think they need to run it more often than strictly needed. In any event, still valid to do so. -
thepudds over 4 yearsFWIW, it is fairly dangerous to try to format this yourself, and you can get it subtly wrong in a way that bites you later. Much better to let the 'go' command do it for you, as described in stackoverflow.com/a/57315225/11210494
-
SteveCoffman over 4 yearsThis is very useful! If you want to Inject build-time variables with Golang into a binary then this is as good a way to figure it out as I've found!
-
Jacob over 4 years@typical182 Can you please test
github.com/docker/[email protected]
withgo get
? I'd serious love to know how to usego get
to create the psuedo version for that package. I recommend verifying that it works. Just running what you'd expect,go get github.com/docker/docker/[email protected]
, does not work sincebut does not contain package github.com/docker/docker/engine
. If any of thego
commands I tried had worked before posting this, i would not have shared this, i absolutely would have preferred usinggo
. If you have a solution usinggo get
, please share! -
thepudds over 4 yearsDocker is a complex case. It probably makes sense for you to open a new question? If you comment here with a link, I will try to answer there.
-
nckturner over 3 yearsWhat if those pseudo versions are in replace directives, which is required in a project importing Kubernetes dependencies (I think)?
-
Dave C almost 3 yearsNote that as of Go1.16 build commands such as
go build
andgo test
behave as if-mod=readonly
was used and will no longer automatically updatego.mod
(as mentioned in your second bullet point of Daily Workflow). You can use-mod=mod
to allow the command to modifygo.mod
as before. (TheGOFLAGS
environment variable can be used to set default flags to Go commands if desired). -
Dave C almost 3 yearsThe canonical way to add such a
require
line togo.mod
is viago get
, e.g.go get golang.org/x/net@161cd47e91fd
(or justgo get golang.org/net
for@latest
).