I tried to setup a new Go project using subdirectories (using internals).
Directory structure look like this:

Root directory: /Users/xyz/code/ppPrinter

.
├── go.mod
├── internal
│   ├── backends
│   │   └── bar.go
│   └── commands
└── main.go

Go mod:

module bitbucket.org/foo/ppprint.git

go 1.22.5

main.go:

package main

import (
    "fmt"

    be "bitbucket.org/foo/ppPrint.git/internal/backends"
)

// Hello returns a greeting for the named person.
func main() {
    // Return a greeting that embeds the name in a message.
    foo := be.Hello("Gladys")
    message := fmt.Sprintf("Hi, %v. Welcome!", name)
    return message
}

bar.go:

package backends

import "fmt"

// Hello returns a greeting for the named person.
func Hello(name string) string {
    // Return a greeting that embeds the name in a message.
    message := fmt.Sprintf("Hi, %v. Welcome!", name)
    return message
}

On my system there an no GO* env variables set by default: env | grep GO returns nothing.

Running main.go:

cd $HOME/code/ppPrinter/ && go run main.go
main.go:6:2: no required module provides package bitbucket.org/foo/ppPrint.git/internal/backends; to add it:
    go get bitbucket.org/foo/ppPrint.git/internal/backends

Same error when setting GOPATH to $HOME/code/ppPrinter.
What am I missing (I just want to be able to structure my local project in subdirectories) ?