Can I have multiple packages inside a single go module? How?

Question

I have a Go module whose name is 'tatata'. It is only developed in my machine and thus it does not contain any path to any URL in the module name.

If I have only one main package in my module it works correctly. However, if I create two packages in the module, I am experiencing some problems.

This is the tree:

./|
  |- go.mod
  |-src
     |- main
     |   | - main.go
     |
     |- api
         | - api.go

The content of the files:

go.mod

module tatata

go 1.13

main.go

package main

import "fmt"
import "tatata/api"

func main() {
  fmt.Println("Hello world")
  api.Test1()
}

api.go

package api

import "fmt"
func Test1() {
   fmt.Println("Testing API")
}

When I try to build, I issue go build ./src/main and I get the following error: build tatata/src/main: cannot load tatata/api: malformed module path "tatata/api": missing dot in first path element

Now, if I try to put a dummy dot, like renaming the module to tatata.com I get the error build tatata.com/src/main: cannot load tatata.com/api: cannot find module providing package tatata.com/api as obviously my package/module is not available in that URL.

GOPATH is empty, i.e. not set.

Questions:

a) What is the right way, i.e. naming of modules and imports when using multiple packages inside a single Go module?

b) Is it impossible to have a Go module without dots in its name?!

c) Can you point me to any working example that has a building set-up with a single go module and multiple packages in the module?

You are missing the src segment: `import "tatata.com/src/api"`. — Peter, Feb 20 '20 at 13:28
Start by removing the `src` folder. Such stuff does not belong into a module. And would make your import path valid. — Volker, Feb 20 '20 at 13:45
There is a good overview of how to structure your module, packages, and files here: https://stackoverflow.com/a/57314494/11210494 — thepudds, Mar 25 '22 at 20:50

score 11 · Answer 1 · answered Feb 20 '20 at 13:48

11

Can I have multiple packages inside a single go module?

Yes, of course.

How?

You have to do nothing, it just works.

(Your problem is: You try to import your api package by a wrong name. Import paths inside a module are of the form <modulename>/<relative-filepath-from-module-root>.)

answered Feb 20 '20 at 13:48

Volker

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Which means the import should have been: import "tatata/src/api" – Dan Ortega Oct 09 '20 at 16:31
The import statement format is different if the package is inside a directory and not in the same directory where module's go.mod file is present then I found following import format works import ( /). E.g. To use stringutils (which is inside directory string) in the module github.com/alessiosavi/GoGPUtils. Use import ( stringutils "github.com/alessiosavi/GoGPUtils/string") – Akshay Hiremath Feb 20 '22 at 22:59

score 3 · Answer 2 · answered Feb 20 '20 at 15:45

3

You can have as many package as you want in a single module, have a look here: https://github.com/alessiosavi/GoGPUtils/

The only constraint is that you cane have a single package for every folder.

answered Feb 20 '20 at 15:45

alessiosavi

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score 1 · Answer 3 · answered Feb 20 '20 at 14:52

1

I found the problem. The go.mod file has to be in the folder that contains the packages. In my case it was in the parent of that folder. Now working.

answered Feb 20 '20 at 14:52

Jose

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Can I have multiple packages inside a single go module? How?

3 Answers3

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