go - How to use "internal" packages?

Question

I try understand how to organize go code using "internal" packages. Let me show what the structure I have:

project/
  internal/
    foo/
      foo.go # package foo
    bar/
      bar.go # package bar
  main.go

# here is the code from main.go
package main

import (
  "project/internal/foo"
  "project/internal/bar"
)

project/ is outside from GOPATH tree. Whatever path I try to import from main.go nothing works, the only case working fine is import "./internal/foo|bar". I think I do something wrong or get "internal" package idea wrong in general. Could anybody make things clearer, please?

UPDATE

The example above is correct the only what I need was to place project/ folder under $GOPATH/src. So the thing is import path like the project/internal/foo|bar is workable if we only import it from project/ subtree and not from the outside.

Answer 1

Waitting for answers