Go: import package from the same module in the same local directory

I want to create new package mycompany that will be published on Github at github.com/mycompany/mycompany-go (something similar to stripe-go or chargebee-go for example).

So I have created a folder ~/Desktop/mycompany-go on my MacOS. Then inside that folder I run go mod init github.com/mycompany/mycompany-go.

I have only these files in that local folder:

// go.mod
module github.com/mycompany/mycompany-go

go 1.19

// something.go
package mycompany

type Something struct {
  Title string
}

// main.go
package main

import (
  "github.com/mycompany/mycompany-go/mycompany"
)

func main() {
  s := mycompany.Something {
    Title: "Example",
  }
}

However I get this error:

$ go run main.go 
main.go:4:3: no required module provides package github.com/mycompany/mycompany-go/mycompany; to add it:
	go get github.com/mycompany/mycompany-go/mycompany

I think that this is a wrong suggestion, because I need to use the local version, in the local folder, not get a remote version.

Basically I need to import a local package, from the same folder, from the same module.

What should I do? What's wrong with the above code?

You can't mix multiple packages in the same folder.

If you create a folder mycompany and put something.go inside it, that should fix the problem

The Go tool assumes one package per directory. Declare the package as main in something.go.

-- main.go --

package main

import "fmt"

func main() {
	s := Something{
		Title: "Example",
	}
	fmt.Println(s)
}

-- go.mod --

module github.com/mycompany/mycompany-go

go 1.19

-- something.go --

package main

type Something struct {
	Title string
}

Runnable example: https://go.dev/play/p/kGBd5etzemK