go mod: cannot find module providing package

Question

I am creating a go project with version 1.12.1. If I run GOPATH="$(pwd)/vendor:$(pwd)" GOBIN="$(pwd)/bin" go clean I get the following error:

can't load package: package github.com/marvincaspar/go-example: unknown import path "github.com/marvincaspar/go-example": cannot find module providing package github.com/marvincaspar/go-example

This is only for go clean, go run or go build works fine.

Here is the folder structure of main code:

.
├── Makefile
├── cmd
│   └── server
│       └── main.go
├── go.mod
├── go.sum
└── pkg
    └── storage
        └── mysql
            └── storage.go

Here is how the go.mod file looks like:

module github.com/marvincaspar/go-example
go 1.12

require (
    github.com/go-sql-driver/mysql v1.4.1
)

And finally the main.go file:

package main

import (
    "fmt"
    "os"

    "github.com/marvincaspar/go-example/pkg/storage/mysql"
)

func main() {
    if err := run(); err != nil {
        fmt.Fprintf(os.Stderr, "%v", err)
        os.Exit(1)
    }
}

func run() error {
    // init storage
    s := mysql.NewStorage()
    // do some other stuff...
}

Any ideas what I am doing wrong?

Answer 1

Go build/install is trying to find main package in your root directory, it is not checking sub-directories (cmd/server) in your case. Hence you are getting package not found error.

To properly build your code, you can run:

go build github.com/marvincaspar/go-example/cmd/server

Similarly, to run your project, you will have to provide module-name/main-package-path:

go run github.com/marvincaspar/go-example/cmd/server

Go clean can be executed in same way, by providing module-name/path-with-main-package

go clean github.com/marvincaspar/go-example/cmd/server

or

GOPATH="$(pwd)/vendor:$(pwd)" GOBIN="$(pwd)/bin" go clean github.com/marvincaspar/go-example/cmd/server 

However, as per https://blog.learngoprogramming.com/code-organization-tips-with-packages-d30de0d11f46, just put your source files into your project’s root. It’s better that way.