(Older toolchains ignore `//go:debug` directives entirely.)

The defaults that will be compiled into a main package
are reported by the command:

{{raw `
	go list -f '{{.DefaultGODEBUG}}' my/main/package
`}}

Only differences from the base Go toolchain defaults are reported.

When testing a package, `//go:debug` lines in the `*_test.go`
files are treated as directives for the test's main package.

pkg go/types, method (*Package) Scope() *Scope
pkg go/types, method (*Package) SetImports([]*Package)
pkg go/types, method (*Package) String() string
pkg go/types, method (*PkgName) Exported() bool
pkg go/types, method (*PkgName) Id() string
pkg go/types, method (*PkgName) Imported() *Package
pkg go/types, method (*PkgName) Name() string
pkg go/types, method (*PkgName) Parent() *Scope
pkg go/types, method (*PkgName) Pkg() *Package