将go项目部署到heroku错误：在以下任何位置都找不到软件包

I've seen many people with similar problems posted on SO, but no solutions have worked for me so far. I'm trying to use govendor to deploy. My file setup:

vendor
  /github.com
    /gorilla
      /websockets
  vendor.json
Procfile (only text is "web: [my_app_name]")    
MyAppBinaryFile

This is my vendor.json file:

{
  "comment": "",
  "ignore": "test",
  "package": [],
  "heroku": {
    "install" : [ "./..." ],
    "goVersion": "go1.9"
  },
  "rootPath": "github.com/[my_acct]/hackernews"
}

This is my GOPATH: GOPATH="/Users/[my_account_name]/go"

This is my GOROOT: GOROOT="/usr/local/Cellar/go/1.10.2/libexec"

This is my error:

remote: -----> Go app detected
remote: -----> Fetching jq... done
remote: -----> Checking vendor/vendor.json file.
remote:  !!
remote:  !!    Deprecated or unsupported version of go (go1.9.4)
remote:  !!    See https://devcenter.heroku.com/articles/go-support#go-versions for supported version information.
remote:  !!
remote: -----> Installing go1.9.4
remote: -----> Fetching go1.9.4.linux-amd64.tar.gz... done
remote: -----> Fetching govendor... done
remote: -----> Fetching any unsaved dependencies (govendor sync)
remote: -----> Running: go install -v -tags heroku ./...
remote: websockets/service.go:9:2: cannot find package "github.com/gorilla/websocket" in any of:
remote:     /tmp/tmp.VCgbsN65Ud/.go/src/github.com/[my_app]/hackernews/vendor/github.com/gorilla/websocket (vendor tree)
remote:     /app/tmp/cache/go1.9.4/go/src/github.com/gorilla/websocket (from $GOROOT)
remote:     /tmp/tmp.VCgbsN65Ud/.go/src/github.com/gorilla/websocket (from $GOPATH)

I have my binary here, not in the /bin directory, although I've copied this file to the /bin directory as well with no luck.

I've followed the heroku tutorial, and can build/deploy their sample app (https://devcenter.heroku.com/articles/getting-started-with-go#deploy-the-app). I've tried changing to godep and even glide.

This issue (https://github.com/heroku/heroku-buildpack-go/issues/136) looks very similar from the logs outputting the error, but I my /vendor file is checked in.

Any help is appreciated, thanks!