standard library in the src/vendor and src/cmd/vendor directories.

There are two modules, std and cmd, defined in src/go.mod and
src/cmd/go.mod. When a package outside std or cmd is imported
by a package inside std or cmd, the import path is interpreted
as if it had a "vendor/" prefix. For example, within "crypto/tls",
an import of "golang.org/x/crypto/cryptobyte" resolves to
"vendor/golang.org/x/crypto/cryptobyte". When a package with the

	// Deprecated: Use PAXRecords instead.
	Xattrs map[string]string

	// PAXRecords is a map of PAX extended header records.
	//
	// User-defined records should have keys of the following form:
	//	VENDOR.keyword
	// Where VENDOR is some namespace in all uppercase, and keyword may
	// not contain the '=' character (e.g., "GOLANG.pkg.version").
	// The key and value should be non-empty UTF-8 strings.
	//

// For example, on return:
//
//	w.importMap["math"] = "math"
//	w.importDir["math"] = "<goroot>/src/math"
//
//	w.importMap["golang.org/x/net/route"] = "vendor/golang.org/x/net/route"
//	w.importDir["vendor/golang.org/x/net/route"] = "<goroot>/src/vendor/golang.org/x/net/route"
//
// Since the set of packages that exist depends on context, the result of
// loadImports also depends on context. However, to improve test running time