This sounds stupid, but I am trying for build my new golang project for a while now and I am stuck with following error
can't load package: package github.com/kuskmen/yamq/cmd/yamq-client: found packages main (main.go) and yamqclient (yamq-client.go) in C:\projects\yamq\cmd\yamq-client
I know this should be straightforward to fix, but I come from .NET and I am still not experienced in Go projects and its dependency resolution model hence the struggle.
My project structure looks like so
/yamq
/cmd
/yamq-client // yamq client application binary
main.go // package main
yamq-client.go // package yamqclient
/yamq-server // yamq server application binary
main.go // package main
yamq-server.go // package yamqserver
go.mod // contains only "module github.com/kuskmen/yamq" for now
... // some library files that will probably be moved to /shared folder
so far so good, when I do go build in outermost directory ( /yamq ) it is building successfully (or at least it is not showing any errors), but when I try to build either yamq-client or yamq-server binaries I get the aforementioned error and every time I try to google it or find something useful I got some old article or answer that dates back 2013-2016 that suggests something about $GOPATH and etc which shouldn't be the case here since I am trying to use go modules.
Help a fellow .NET developer join Go community by explaining him how exactly modules work cause I found this and this useless or at least I am missing the point, thanks in advance!
To follow up from my comment above:
From https://golang.org/doc/code.html:
Go programmers typically keep all their Go code in a single workspace.
A workspace contains many version control repositories (managed by Git, for example).
Each repository contains one or more packages.
Each package consists of one or more Go source files in a single directory.
The path to a package's directory determines its import path.
For your project, I'd do something like this:
$ tree
.
├── clientlib
│ └── lib.go
├── cmd
│ ├── client
│ │ └── main.go
│ └── server
│ └── main.go
├── go.mod
└── serverlib
└── lib.go
5 directories, 5 files
$ cat go.mod
module myproject.com
The module name is arbitrary (could be github.com/yourname/yourproject).
For the server side:
$ cat serverlib/lib.go
package serverlib
import "fmt"
func Hello() {
fmt.Println("Hello from serverlib.Hello")
}
$ cat cmd/server/main.go
package main
import (
"fmt"
"myproject.com/serverlib"
)
func main() {
fmt.Println("Running server")
serverlib.Hello()
}
And now we can build and run it:
$ go build -o server cmd/server/main.go
$ ./server
Running server
Hello from serverlib.Hello
The client side looks symmetrical.
Variations: you could name the .go files in cmd/... by their actual binary names - like server.go and client.go. The package in each is still main, but then go build creates an executable with the file's name (sans the .go) without needing to -o explicitly.
Related
I have multiple Go projects (and all of them are also Go modules) all in a folder. They are all HTTP servers and exchanging REST calls, thus, I need all of them up and running simultaneously.
So, for local testing purposes, I thought it would be reasonable to run all of them from the parent instead of moving all of the project root directories and running go run main.go in multiple terminals.
container_dir/
├── prj1/
│ ├── go.mod
│ ├── main.go
│ └── ...
├── prj2/
│ ├── go.mod
│ ├── main.go
│ └── ...
└── ...
Here are some some commands I have tried and the error messages for each time:
container_dir $ go run ./*/*.go
##ERROR: named files must all be in one directory; have ./prj1/ and ./prj2/
container_dir $ go run *.go
##ERROR: stat *.go: no such file or directory
container_dir $ go run ./prj1 ./prj2/
##ERROR: cannot find package "github.com/jackc/pgx/v4" in any of:
/usr/local/go/src/github.com/jackc/pgx/v4 (from $GOROOT)
/home/user/go/src/github.com/jackc/pgx/v4 (from $GOPATH)
cannot find package ...
So, I can give a final rephase for the question: How to run multiple go modules in sibling directories when they have some third party dependencies etc.?
P.S: As possible with Go modules suggest container_dir for my projects is in an arbitrary location and I expect no $GOPATH relevance.
Go version: 1.13.6
Don't use go run outside of tiny, playground-style tests
Source paths are a compile-time concern and are irrelevant at runtime - being in "sibling directories" doesn't mean anything when the program is running
go run runs a single program; just like building a program and running its executable binary (which is what go run does) runs a single program.
Looks like your go.mod stuff is having problems dude.
remember you can do replace inside it and reference your other application
module container_dir/prj2
go 1.13
require(
container_dir/prj1 v0.0.0
)
replace (
container_dir/prj1 => ../prj1
)
require is the path you import but it'll get switched to the relative path on build.
This question is in reference to the popular project-layout.
Is this simply a way to lay out the code, but the actual compilation of a binary will be in the
/cmd/app1/
/cmd/app2/
So if I have a website, it would still be considered a cmd application that would simply start the http listener etc.
Or are there several "entry" points throughout the layout and not just in the cmd folders?
How exactly would you actual build and run your application using this layout? (or one of them since from what I understand it supports multiple)
is it like:
go build cmd/app1/*.go ?
You can just
go build ./cmd/app/
For example I have this module
├── cmd
│ ├── cli
│ │ └── main.go
│ └── web
│ └── main.go
├── go.mod
└── service
└── service.go
go.mod is just
module example
service.go:
package service
import "fmt"
func DoSomething() {
fmt.Println("service processing")
}
cmd/web/main.go:
package main
import (
"example/service"
"fmt"
)
func main() {
fmt.Println("starting web program")
service.DoSomething()
}
cmd/cli/main.go:
package main
import (
"example/service"
"fmt"
)
func main() {
fmt.Println("starting cli program")
service.DoSomething()
}
Build (From root)
Build web:
go build ./cmd/web/
This will create binary file web
run web
./web
// output:
// starting web program
// service processing
Build cli:
go build ./cmd/cli/
run web
./web
// output:
// starting cli program
// service processing
If you want to build all of your apps inside a folder you can do like this :
go install ./...
this will build all your apps in bin folder inside GOPATH then you can run whatever app you like.
But if you want to build and run a specific app you can go to that folder and simply run.
go build
As long as there is a main package in that folder you can build your program.
I am trying to build a micro-services architecture project in Go. I am currently using Go 1.11 which supports modules, so I put my root directory in an arbitrary chosen directory, outside of GOPATH.
If I am getting the micro-services architecture concepts right, although my microservices need to be independent, they can share dependencies (and I don't see another way to do stuff, is it?)
Below is my directory structure:
.
├── go.mod
├── lambda
│ └── account_create
│ └── main.go
├── readme.md
└── types
├── account.go
├── location.go
├── order.go
├── pricing.go
├── product.go
└── types.go
Now the behavior I expected was to be able to run go build lambda/account_create and get an executable with that functionality so I can supply it to the respective AWS Lambda function.
However, when I run the command, I get:
can't load package: package lambda/account_create: unknown import path "lambda/account_create": cannot find module providing package lambda/account_create
Please explain me why this does not work and give me some advice on how a project like this should look.
Thank you very much!
Edit Here is my lambda/account_create/main.go file contents:
package account_create
import (
"fmt"
"roasted.ro/pkg/types"
)
func main() {
account := types.UserAccount{Name: "Victor"}
fmt.Printf("Welcome %s", account.Name)
}
To answer the latter part of your question (as the first half is more about preference), you need to do:
go build ./lambda/account_create
Notice the ./. go build takes in a package name or a path. If you don't prepend the path with a ./, it assumes you are giving it a package name.
Edit: the package has to be main if you want an executable. According to the docs, you always have to use package main for projects that build an executable:
Executable commands must always use package main.
Edit: I'll add some opinions on layout:
Consider which parts of your project are exported to other go projects. Meaning someone could import your package and expect to gain value and not have their code break when yours changes.
That should be either in a github.com/you/pkg/somepath package or just github.com/you/somepath.
Anything else (other than main packages) should be under a /internal package.
I typically make a /cmd/myexecurable1 /cmd/myexecurable2 and so forth for each executable.
I want to break my project up to subfolders.
I want this code structure:
├── main.go
└── models
└── user.go
Where main.go is:
package main
import (
"fmt"
"./models"
)
func main(){
fmt.Println(User{"new_user"})
}
And user.go is:
package models
type User struct {
Login string
}
But User is not defined in main package and import raise warning "imported and not used".
What am I doing wrong? My project is simple (not such a example but just with few files (controllers and models)) and I want a simple structure.
Maybe I doing it in completely wrong way?
Problem project is here: https://github.com/abonec/go_import_problem
I recently achieved this by using go modules.
Golang introduced preliminary opt-in support for modules as of go v1.11.1 which is intended to completely remove the, frankly, absurd $GOPATH necessity. Not only can you now have versioned dependencies in any normal directory such as ~/development, but you can basically have something that looks like namespaces and sub-directories. You can enable this feature by invoking the go command with the following environment variable: GO111MODULE=on.
Go v1.11.3 expects to enable modules by default and is slated for August 2019.
Here is an example directory structure (that you might find typically in some other languages).
~/Dev/my-app
├── src/
│ ├── one/
│ │ ├── two/
│ │ │ └── two.go
│ │ └── one.go
│ └── zero.go
├── go.mod
└── app.go
The application is called my-app, which will be the module name for app.go. We define this once in go.mod and then each of all the other go files in subdirectories will automatically be importable as if they were namespaced.
Given the above, two.go, assuming it contains a function named Two, will be importable in app.go by using my-app/src/one/two.
Here's what you need to do to achieve this:
go.mod
module my-app
two.go
package two
func Two() string {
return "I'm totally not supposed to be using go modules for this"
}
app.go
package main
import "my-app/src/one/two"
func main() {
two.Two()
}
If you were to place another file within two/, then you would simply use two.TheNewFunc() as long as you made TheNewFunc() available within the new file.
I created a very simple GitHub repo which you can check out as a demonstration.
Your import should be an absolute one:
import "github.com/abonec/go_import_problem/models"
If you don't want to export your project to an external referential, you can do a:
import "go_import_problem/models"
(That is: "the name of your project folder accessible by GOPATH/your package")
See "How to use custom packages in golang?".
And you would use:
models.User
As mentioned in Effective Go:
The importer of a package will use the name to refer to its contents, so exported names in the package can use that fact to avoid stutter.
(Don't use the import . notation, which can simplify tests that must run outside the package they are testing, but should otherwise be avoided.)
kostix adds in the comments:
to reiterate, names of Go packages are always absolute (that is, there's no relative package names, neither with ./ nor with ../ or anything like that) but that names are "anchored" to one of the so-called workspaces listed in $GOPATH.
When Go searches for a package, it looks through workspaces and tries to find a package in each of them, in order.
The search is not recursive.
And no, there's no requirement to encode URLs in package paths -- unless you want to make your package public.
You need to qualify items in in a package by its package name
So
fmt.Println(models.User{"new_user"})
Breaking up a single project into subfolders is not the recommended way of structuring a go project, which is why there is basically no good way to do what you want.
If the project is really large, and too unwieldy to make a single package, consider splitting it into several totally distinct packages, rather than special sub-directory packages. This has the advantage of forcing you to think cleanly about your internal APIs.
The packages are referenced in code in relation to your "go/src" folder
└── go
└── src
└── myAwesomeProject
├── main.go
└── models
└── user.go
So in main.go
package main
import (
"fmt"
"myAwesomeProject/models"
)
Similarly packages can reference each other using the same convention.
You should use your imported objects by it's imported names. For example if you
import "./models"
with struct User you should use it as
models.User
I want to break my project up to subfolders.
I want this code structure:
├── main.go
└── models
└── user.go
Where main.go is:
package main
import (
"fmt"
"./models"
)
func main(){
fmt.Println(User{"new_user"})
}
And user.go is:
package models
type User struct {
Login string
}
But User is not defined in main package and import raise warning "imported and not used".
What am I doing wrong? My project is simple (not such a example but just with few files (controllers and models)) and I want a simple structure.
Maybe I doing it in completely wrong way?
Problem project is here: https://github.com/abonec/go_import_problem
I recently achieved this by using go modules.
Golang introduced preliminary opt-in support for modules as of go v1.11.1 which is intended to completely remove the, frankly, absurd $GOPATH necessity. Not only can you now have versioned dependencies in any normal directory such as ~/development, but you can basically have something that looks like namespaces and sub-directories. You can enable this feature by invoking the go command with the following environment variable: GO111MODULE=on.
Go v1.11.3 expects to enable modules by default and is slated for August 2019.
Here is an example directory structure (that you might find typically in some other languages).
~/Dev/my-app
├── src/
│ ├── one/
│ │ ├── two/
│ │ │ └── two.go
│ │ └── one.go
│ └── zero.go
├── go.mod
└── app.go
The application is called my-app, which will be the module name for app.go. We define this once in go.mod and then each of all the other go files in subdirectories will automatically be importable as if they were namespaced.
Given the above, two.go, assuming it contains a function named Two, will be importable in app.go by using my-app/src/one/two.
Here's what you need to do to achieve this:
go.mod
module my-app
two.go
package two
func Two() string {
return "I'm totally not supposed to be using go modules for this"
}
app.go
package main
import "my-app/src/one/two"
func main() {
two.Two()
}
If you were to place another file within two/, then you would simply use two.TheNewFunc() as long as you made TheNewFunc() available within the new file.
I created a very simple GitHub repo which you can check out as a demonstration.
Your import should be an absolute one:
import "github.com/abonec/go_import_problem/models"
If you don't want to export your project to an external referential, you can do a:
import "go_import_problem/models"
(That is: "the name of your project folder accessible by GOPATH/your package")
See "How to use custom packages in golang?".
And you would use:
models.User
As mentioned in Effective Go:
The importer of a package will use the name to refer to its contents, so exported names in the package can use that fact to avoid stutter.
(Don't use the import . notation, which can simplify tests that must run outside the package they are testing, but should otherwise be avoided.)
kostix adds in the comments:
to reiterate, names of Go packages are always absolute (that is, there's no relative package names, neither with ./ nor with ../ or anything like that) but that names are "anchored" to one of the so-called workspaces listed in $GOPATH.
When Go searches for a package, it looks through workspaces and tries to find a package in each of them, in order.
The search is not recursive.
And no, there's no requirement to encode URLs in package paths -- unless you want to make your package public.
You need to qualify items in in a package by its package name
So
fmt.Println(models.User{"new_user"})
Breaking up a single project into subfolders is not the recommended way of structuring a go project, which is why there is basically no good way to do what you want.
If the project is really large, and too unwieldy to make a single package, consider splitting it into several totally distinct packages, rather than special sub-directory packages. This has the advantage of forcing you to think cleanly about your internal APIs.
The packages are referenced in code in relation to your "go/src" folder
└── go
└── src
└── myAwesomeProject
├── main.go
└── models
└── user.go
So in main.go
package main
import (
"fmt"
"myAwesomeProject/models"
)
Similarly packages can reference each other using the same convention.
You should use your imported objects by it's imported names. For example if you
import "./models"
with struct User you should use it as
models.User