Imports golang.org/x/build/envutil golang.org/x/build/internal/httpdl golang.org/x/build/pargzip cloud.google.com/go/compute/metadata golang.org/x/build golang.org/x/build/revdial golang.org/x/build/buildlet Standard library imports crypto/hmac crypto/sha1 archive/tar compress/gzip crypto/md5 net/url os bufio bytes crypto/tls crypto/x509 encoding/json errors flag fmt io io/ioutil log net os/exec path path/filepath regexp net/http runtime strconv strings time