internal/tools/go/loader cannot load package in vendor dir?

[yangxikun]

I run pythia -open=false github.com/fzipp/pythia, but got error:

/home/rokety/Software/go/src/net/http/h2_bundle.go:45:2: could not import golang_org/x/net/http2/hpack (cannot find package "golang_org/x/net/http2/hpack" in any of:
        /home/rokety/Software/go/src/golang_org/x/net/http2/hpack (from $GOROOT)
        /home/rokety/Software/go-app/src/golang_org/x/net/http2/hpack (from $GOPATH))
/home/rokety/Software/go/src/net/http/h2_bundle.go:848:19: undeclared name: hpack

my go version is 1.7.4