How can I automatically add dependency packages to go.mod

Question

I have modifed an existing github project with dozens of 3rd party imported packages but I kept the basic structure intact, which is like this:

.
├── config
│   ├── config.json
│   └── mysql.sql
├── gowebapp.go
├── LICENSE
├── README.md
├── static
├── template
│   ├── about
│   │   └── about.tmpl
│   ├── base.tmpl
└── vendor
    └── app
        ├── controller
        │   ├── about.go
        │   ├── error.go
        │   ├── index.go
        │   ├── login.go
        │   ├── notepad.go
        │   ├── register.go
        │   └── static.go
        ├── model
        │   ├── model.go
        │   ├── note.go
        │   └── user.go
        ├── route
        │   ├── middleware
        │   │   ├── acl
        │   │   │   └── acl.go
        │   │   ├── httprouterwrapper
        │   │   │   └── httprouterwrapper.go
        │   │   ├── logrequest
        │   │   │   └── logrequest.go
        │   │   └── pprofhandler
        │   │       └── pprofhandler.go
        │   └── route.go
        └── shared
            ├── database
            │   └── database.go
            ├── email
            │   └── email.go
            ├── jsonconfig
            │   └── jsonconfig.go
            ├── passhash
            │   ├── passhash.go
            │   └── passhash_test.go
            ├── recaptcha
            │   └── recaptcha.go
            ├── server
            │   └── server.go
            ├── session
            │   └── session.go
            └── view
                ├── plugin
                │   ├── noescape.go
                │   ├── prettytime.go
                │   └── taghelper.go
                └── view.go

Now I want to use go modules to make the project portable.

The main.go imports are like:

    package main

    import (
    "encoding/json"
    "log"
    "os"
    "runtime"

    "app/route"
    "app/shared/database"
    "app/shared/email"
    "app/shared/jsonconfig"
    "app/shared/recaptcha"
    "app/shared/server"
    "app/shared/session"
    "app/shared/view"
    "app/shared/view/plugin"
)

As you can see the code mostly sits in vendor/app folder.

I have added several other packages to that.

The problem is that manually adding the packages to go.mod is so tedious, and after all I may miss some imports.

So I'm wondering if there are some automatic tricks to fetch the dependencies to go.mod?

Varicolored

Answer 1

Initialize the module with go mod init module-path, this will create the go.mod file. Build the project with go build. It automatically adds all dependencies to go.mod, transitively.

No manual step is involved. The go tool does everything for you. Of course you may edit the go.mod file and "fine-tune" the included versions if the automatically chosen ones do not fit your need / intent. See Version Selection how it is done by default.

Note that starting with Go 1.16, go mod tidy might be needed to add depencencies.

Kurtkurth

Well I get this error: build proj1: cannot load app/route: malformed module path "app/route": missing dot in first path element – Varicolored

Then fix that error first. You have to use full import path, with module path prefixed. E.g. if your module has path github.com/joe, and your module contains app/route folder, you have to import that as github.com/joe/app/route, and not just as app/route. – Kurtkurth

Actually app/route is located in /home/me/go/src/proj1/vendor/app/route. So how should I modify the import to be useful? – Varicolored

vendor is special, it is only used if you pass -mod=vendor, but then all your deps should be vendored. Decide what you want. If you don't want to vendor all your deps, then move app/route to the project root or to another module which you can import properly. To use a folder on your disk, see How to use a module that is outside of “GOPATH” in another module? – Kurtkurth

Well, the project from github github.com/josephspurrier/gowebapp and modified the code heavily. As you can see most of th code is in vendor but inside that there are imports from github and google. So what why do you suggest me to do to add go.mod with the least re-structuring? – Varicolored

You may try go mod vendor which downloads all dependencies into the vendor folder. But your setup seem like it asks for trouble itself. "don't like github imports" is not a valid argumentation here. You're not making your life easier. – Kurtkurth

@Varicolored Sorry, it's go mod vendor. But you should not force workarounds, you should try to properly import existing dependencies. – Kurtkurth

Still get error: module-path imports app/route: malformed module path "app/route": missing dot in first path element – Varicolored

@Varicolored Yes, go mod vendor can only download properly imported packages. – Kurtkurth

So please tell me how to modify the imports properly. I'm just using the gowebapp imports which are like import ( "net/http" "app/shared/session" "app/shared/view" ) see:github.com/josephspurrier/gowebapp/blob/master/vendor/app/… – Varicolored

Modify the imports to be valid. app/shared/view is not a valid import path if there is no module and its package denoted by this path. – Kurtkurth

Sorry, it's not clear to me. Can you give me an example, for example what should be the correct import instead of "app/route"? The project was built and runnig fine before I added go.mod. – Varicolored

The import path must point to a valid package. If there is a published repo such as github.com/icza/bito, that is a valid import path. The path this.leads.to.nowhere/invalid is not a valid import path, there is no repository hosted there. If you use the replace directive in go.mod (see linked answer in my previous comment), you may designate any path to point to an existing package in your disk, then that will also be a valid import path. – Kurtkurth

So how would you replace "app/route" in my case where I have downloaded github.com/josephspurrier/gowebapp and modifed the code base? Please give me an example instead of lectures. – Varicolored

@Varicolored That depends how where you put it, and what have you modified in it. Have you thought about that you could learn more from lectures than from a direct answer without reasoning? – Kurtkurth

I have added some controllers, routes and models. I did not change the basic structure of the gowebapp, and I'm still in dark on how to modify the imports in order to make it modules-friendly. – Varicolored

Answer 2

go mod tidy

Run that command is the short answer

Holston

Thank you, the accepted answer is almost inintelligible :D – Cybele