utils/importer.go
func MakeUniversalImporter(searchUrls []*url.URL) jsonnet.Importer {
	// Reconstructed copy of http.DefaultTransport (to avoid
	// modifying the default)
	t := &http.Transport{
		Proxy: http.ProxyFromEnvironment,
		DialContext: (&net.Dialer{
			Timeout:   30 * time.Second,
			KeepAlive: 30 * time.Second,
			DualStack: true,
		}).DialContext,
		MaxIdleConns:          100,
		IdleConnTimeout:       90 * time.Second,
		TLSHandshakeTimeout:   10 * time.Second,
		ExpectContinueTimeout: 1 * time.Second,
	}

	t.RegisterProtocol("file", http.NewFileTransport(http.Dir("/")))
	t.RegisterProtocol("internal", http.NewFileTransport(newInternalFS("lib")))

	return &universalImporter{
		BaseSearchURLs: searchUrls,
		HTTPClient:     &http.Client{Transport: t},
		cache:          map[string]jsonnet.Contents{},
	}
}
func MakeUniversalImporter(searchUrls []*url.URL) jsonnet.Importer {
	// Reconstructed copy of http.DefaultTransport (to avoid
	// modifying the default)
	t := &http.Transport{
		Proxy: http.ProxyFromEnvironment,
		DialContext: (&net.Dialer{
			Timeout:   30 * time.Second,
			KeepAlive: 30 * time.Second,
			DualStack: true,
		}).DialContext,
		MaxIdleConns:          100,
		IdleConnTimeout:       90 * time.Second,
		TLSHandshakeTimeout:   10 * time.Second,
		ExpectContinueTimeout: 1 * time.Second,
	}

	t.RegisterProtocol("file", http.NewFileTransport(http.Dir("/")))
	t.RegisterProtocol("internal", http.NewFileTransport(newInternalFS("lib")))

	return &universalImporter{
		BaseSearchURLs: searchUrls,
		HTTPClient:     &http.Client{Transport: t},
		cache:          map[string]jsonnet.Contents{},
	}
}
/*
MakeUniversalImporter creates an importer that handles resolving imports from the filesystem and http/s.

In addition to the standard importer, supports:
  - URLs in import statements
  - URLs in library search paths

A real-world example:
  - you have https://raw.githubusercontent.com/ksonnet/ksonnet-lib/master in your search URLs
  - you evaluate a local file which calls `import "ksonnet.beta.2/k.libsonnet"`
  - if the `ksonnet.beta.2/k.libsonnet`` is not located in the current workdir, an attempt
    will be made to follow the search path, i.e. to download
    https://raw.githubusercontent.com/ksonnet/ksonnet-lib/master/ksonnet.beta.2/k.libsonnet
  - since the downloaded `k.libsonnet`` file turn in contains `import "k8s.libsonnet"`, the import
    will be resolved as https://raw.githubusercontent.com/ksonnet/ksonnet-lib/master/ksonnet.beta.2/k8s.libsonnet
	and downloaded from that location
*/