How to have a global constant accessible in all packages in golang?

Question

I have a constant defined within a package in golang as such:

package services

const (
   Source = "local"
)

I would like to make this constant accessible by other packages without having to import the package into my other module. How can I go about that?

Answer 1

You cannot refer to services.Source without importing services.

However, you can avoid the dependency by creating a new constant in another package that happens to have the same value, and verify that with a test. That is, your test imports services, but your production code does not. The stdlib does this here and there to avoid a few dependencies.

// services.go
package services

const Source = "local"

// foo.go
package foo

const Source = "local"

// foo_test.go
package foo

import (
    "services"
    "testing"
)

func TestSource(t *testing.T) {
    if Source != services.Source {
        t.Error("Source != services.Source")
    }
}