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?

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.

Answer 2

go mod tidy

Run that command is the short answer