Go, Golang : does not make sense that I have to have files before import
I am trying to go to next step but keep getting errors
I have the package that I want to import ready.
All I need to do is to import the external package from github and be able to use it on any code.
So this is what I did.
mkdir $HOME/go
export GOPATH=$HOME/go
go get github.com/user/project
This runs successfully. I downloaded it onto here with source code files from github
/Users/user/go/src/github.com/user/project/project.go
So to use this package that I just import I do
go run /Users/user/Desktop/code.go
But I am getting the following errors
MacBook-Air:~ user$ go run /Users/user/Desktop/code.go
Desktop/code.go:32:8: cannot find package "project" in any of:
/usr/local/go/src/pkg/project (from $GOROOT)
/Users/user/go/src/project (from $GOPATH)
What should I do? AM I missing something? Thanks in advance and please help me. I wrote a lot of code but being very frustrated not being able to distribute it because of this.
The error message says at line 32 in your code.go it can't find package "goling".
Assuming that is a local package you want to use, you need to make sure it is in your GOPATH.
If you set GOPATH then you should develop your code within it, so moving the "goling" directory into /Users/user/go/src is the right thing to do.
Alternatively "goling" could be a typo, so check the imports in code.go. If you want to import an project from github the import should say
import "github.com/user/project"
And you then use the parts of project with a prefix of project.
If that doesn't help you get it working, then post the imports section of code.go.
It looks like you've got the external package in the same folder as your main package which uses it. In go, all packages must be in separate directories. It looks like the github project itself is actually doing that. If you separate the packages into different directories it should work properly.
Related
I'm very new to Golang. I see that in Golang you can import packages directly from Github like:
import "github.com/MakeNowJust/heredoc"
Does that mean I have to remember this URL in order to use this package? IMHO this is not cool. What if later the author of the package removed it or changed the URL? Any ideas?
I would recommend you to read the How to Write Go Code documentation and this blog post.
The path you're seeing in your import line is not a url, but only the path the package is located in (normally relative to $GOROOT/src/pkg or $GOPATH/src). So your package heredoc is most probably located in the directory $GOPATH/src/github.com/MakeNowJust/heredoc.
The recommended way to use external packages is by downloading and installing them via go get. You might want to check out the documentation of go get by go get --help.
The path that import statement refers is just appended to $GOPATH/src. So that import statement basically says "import the package located at $GOPATH/src/github.com/MakeNowJust/heredoc"
What if later the author of the package removed it or changed the URL?
As long as you already have the source files for that package at the expected location, it should be included even if the repo has moved.
dont worry man! you can use glide tool for package management
I'm trying to use import a package for internal use, but I have been having some issues.
My directory structure looks like this:
app/
model/
file1.go
file2.go
...
main.go
When I try to build the program, I get an error that looks something like this:
/usr/local/go/src/pkg/model (from $GOROOT)
I want to be able to call the model programs in any of my other programs in the app simply using:
import "app/model"
What are my options when it comes to doing this?
You import from GOPATH level .. all of your packages should live there.
For example, assuming your application is here:
$GOPATH/src/dtrinh100/app/
..and your package you wish to import is here:
$GOPATH/src/github.com/other/package
Your import would be:
import "github.com/other/package"
You should review the literature around what the GOPATH environment variable is all about. When beginning Go, it is important you understand its purpose and initially, you should place all of your projects/packages inside of the GOPATH.
When you import a custom package, Go looks for its definition in each workspace listed in the GOPATH environment variable. Your custom package should be defined in a src subdirectory.
If you keep your code in a source repository somewhere, then you should use the root of that source repository as your base path. For instance, if you have a GitHub account at github.com/user, that should be your base path.
Note that you don't need to publish your code to a remote repository before you can build it. It's just a good habit to organize your code as if you will publish it someday. In practice you can choose any arbitrary path name, as long as it is unique to the standard library and greater Go ecosystem.
You should use github.com/user as our base path. Create a directory inside your workspace in which to keep source code:
$ mkdir -p $GOPATH/src/github.com/user
You can look at How to Write Go Code for more details.
I am having difficulty in importing a local go file into another go file.
My project structure is like something below
-samplego
--pkg
--src
---github.com
----xxxx
-----a.go
-----b.go
--bin
I am trying to import a.go inside b.go. I tried the following,
import "a"
import "github.com/xxxx/a"
None of these worked..I understand I have to meddle up with GOPATH but I couldn't get it right. Presently my GOPATH is pointing to samplego(/workspace/samplego).I get the below error
cannot find package "a" in any of:
/usr/local/go/src/pkg/a (from $GOROOT)
/workspace/samplego/src/a (from $GOPATH)
Also, how does GOPATH work when these source files are imported into another project/module? Would the local imports be an issue then? What is the best practice in this case - is it to have just one go file in module(with associated tests)?
Any number of files in a directory are a single package; symbols declared in one file are available to the others without any imports or qualifiers. All of the files do need the same package foo declaration at the top (or you'll get an error from go build).
You do need GOPATH set to the directory where your pkg, src, and bin directories reside. This is just a matter of preference, but it's common to have a single workspace for all your apps (sometimes $HOME), not one per app.
Normally a Github path would be github.com/username/reponame (not just github.com/xxxx). So if you want to have main and another package, you may end up doing something under workspace/src like
github.com/
username/
reponame/
main.go // package main, importing "github.com/username/reponame/b"
b/
b.go // package b
Note you always import with the full github.com/... path: relative imports aren't allowed in a workspace. If you get tired of typing paths, use goimports. If you were getting by with go run, it's time to switch to go build: run deals poorly with multiple-file mains and I didn't bother to test but heard (from Dave Cheney here) go run doesn't rebuild dirty dependencies.
Sounds like you've at least tried to set GOPATH to the right thing, so if you're still stuck, maybe include exactly how you set the environment variable (the command, etc.) and what command you ran and what error happened. Here are instructions on how to set it (and make the setting persistent) under Linux/UNIX and here is the Go team's advice on workspace setup. Maybe neither helps, but take a look and at least point to which part confuses you if you're confused.
No import is necessary as long as you declare both a.go and b.go to be in the same package. Then, you can use go run to recognize multiple files with:
$ go run a.go b.go
./main.go (in package main)
./a/a.go (in package a)
./a/b.go (in package a)
in this case:
main.go import "./a"
It can call the function in the a.go and b.go,that with first letter caps on.
If none of the above answers works,
Just try,
go run .
for production,
go build
This will take care of all the .go files in the folder.
I just wanted something really basic to move some files out of the main folder, like user2889485's reply, but his specific answer didnt work for me. I didnt care if they were in the same package or not.
My GOPATH workspace is c:\work\go and under that I have
/src/pg/main.go (package main)
/src/pg/dbtypes.go (pakage dbtypes)
in main.go I import "/pg/dbtypes"
As people mentioned previously, there is no need to use any imports.
A lot of people mention that using go run is possibe when you mention most files, however when having multiple .go-files in the same dir it can be cumbersome.
Therefore using go run *.go is what I usually do.
As I understand for packages in your project subfolders it's possible now to do, just need to add "." in front of module, like
. "github.com/ilyasf/deadlock-train/common"
where github.com/ilyasf/deadlock-train my main module name and common is just package from /common subfolder inside project.
go1.19.1 version here. I've just had the same issue, discovered that you must simply do: import (a "github.com/xxxx")
You can go to the correct folder and execute: $ go run *.go
As long as the code only 1 main function in all files it works perfect!
I wish to learn how to logically split my code in a Go package into multiple files, and crucially, the syntax necessary to use that split/separate file in another file of the same package.
I have created a go project in this form
-test
-bin
-pkg
-src
-main
main.go
test.go
and attempted to run go build main and go build main.go test.go, but I have always got an error.
test.go contains only this code
package main
import "fmt"
func do(b string) {
fmt.Println(b)
}
I want to be able to call do("x") in main.go.
Right now all that is in main.go is
package main
func main() {
test.do("x")
}
I do not know what to do to get this to work. Many answers seem to suggest moving test.go into a directory "test". I am hoping Go does not require me to make a directory for every piece of code I write, but maybe I would be "fighting the system". Many answers have pointed me to a website telling me to make the above directory structure, and to use go install to compile my binaries, but that does not work.
I just want to know how to use functions in package/x.go inside package/y.go, even if they are in the same package. There has to be a way to do this, otherwise I will have either a bunch of unnecessary packages or hard to understand monolithic files.
I know there are many similar questions, but in my searching I haven't been able to find an actual example of the code in two files in the same package that reference each other.
test.go has to be in the same package if is in the same directory. the package is thus main for both of the files and being in the same package you can just call do("x") .
Additionally you can build the entire package like this without specifying the single files.
export GOPATH="<path to>/test"
go build main
Just use:
do
instead of:
test.do
How does one do a relative import from a parent directory?
From meme/cmd/meme:
import "../../../meme"
This gives an ambiguous error:
matt#stanley:~/gopath/src/bitbucket.org/anacrolix/meme/cmd/meme$ go get bitbucket.org/anacrolix/meme/cmd/meme
can't load package: /home/matt/gopath/src/bitbucket.org/anacrolix/meme/cmd/meme/main.go:8:2: local import "../../../meme" in non-local package
matt#stanley:~/gopath/src/bitbucket.org/anacrolix/meme/cmd/meme$ echo $GOPATH
/home/matt/gopath
How do I import locally from a parent directory?
Edit: Relative import paths are not the way to go in Go. Lack of documentation shows something about popularity of relative paths, and I don't see a reason for using them. Go's recommended code organization works pretty well. Every package should have a unique import path and be imported everywhere using that same import path.
See how a package like github.com/ha/doozerd/peer imports its neighbors. This is a common practice among Go projects and I've seen it a lot of times. Package camlistore.org/pkg/auth (also on GitHub; written by one of the main authors of Go) imports camlistore.org/pkg/netutil by full path.
Even if you are having both commands and libraries in the same project this approach works. In your original questions you wisely asked for best practices. I did my best in explaining best practices on this matter.
Import paths can't be relative in Go. I recommend reading How to Write Go Code, the essential reading on organizing Go projects. Here's a short overview:
Make a directory like ~/go for your Go development. Then say:
$ export GOPATH=~/go
$ mkdir $GOPATH/{src,bin,pkg}
$GOPATH/src holds source code for all your Go packages, even the ones your download with go get. bin and pkg keep output of compilations. Packages with package name main are commands and yield to executable binaries which go to $GOPATH/bin. Other packages are libraries and their compiled object files are put in $GOPATH/pkg.
Now if you put your code in $GOPATH/src/matt/meme, you can import it by import "matt/meme". It's recommended to use a prefix for your package names and leave short package names for standard libraries. That's why I used $GOPATH/src/matt/meme instead of $GOPATH/src/meme.
Organize your code around this idea.
Thanks for adding to your question. First, an answer, then some explanation. I built your code by,
go get, just as you had it. (I ignored the error messages.)
setting the import line in main.go back to "../../../meme", as you wanted to do.
(commenting out a little bit of code containing an unused variable.)
then in the meme/cmd/meme directory, either go run main.go or go build main.go worked.
I was wrong in my comment earlier when I said go install works; I should have said go build.
The key however is that go build alone does not work; you must type go build main.go. This is because the go command does not allow "local imports in non-local packages." You are right that spec is of little help here. It weasels out saying, "The interpretation of the ImportPath is implementation-dependent." The current implementation behavior was set with CL 5787055, which was subsequently debated at length on Go-nuts.
"Local" means indicated with a file system relative path. Obviously a relative path starting with .. is local, so the trick is just getting the go command to treat main as a local package as well. It apparently doesn't do this when you type go build, but does when you type go build main.go.
Relarive imports are supported when manually using the compiler, linker, ... directly. The 'go' (build) tool doesn't support the same (somehow comparable to eg Java).
This may not answer the original question, but I was trying to do the above when I didn't really need to, all I needed to do was update go.mod temporarily with a replace :
module github.com/pselle/foo
replace github.com/pselle/bar => /Users/pselle/Projects/bar
require (
github.com/pselle/bar v1.0.0
)
reference:
https://thewebivore.com/using-replace-in-go-mod-to-point-to-your-local-module/