I've seen this comment at the top of a go source file (fixtures.go).
// +build fixtures
package packagename
What does the comment "+build fixtures" mean? Is it a kind of directive? I've googled, but couldn't find any answer.
Running "go test" in the package, fails due to undefined functions that are defined in the file "fixtures.go". If I remove the comment at the top o the file "+build fixtures", tests succeed!
It is part of the official documentation of the build package.
You can find it here