title: go get -> cannot download, /home/azhukov/go is a GOROOT, not a GOPATH
body: <p>Good day! I am trying to install gb (vendoring tool for go) in Google Cloud.
  I try <code>go get</code> and it fails:</p>
  
  <pre><code>azhukov@gce-machine:~$ go get -v github.com/constabulary/gb/...
  package github.com/pkg/errors: cannot download, /home/azhukov/go is a GOROOT, not a GOPATH. For more details see: 'go help gopath'
  </code></pre>
  
  <p>here is env:</p>
  
  <pre><code>azhukov@gce-machine:~$ echo $GOPATH, $GOROOT, $PATH
  /home/azhukov/go, , /usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/usr/local/go/bin:/home/azhukov/go/bin
  </code></pre>
  
  <p>go version:</p>
  
  <pre><code>azhukov@gce-machine:~$ go version
  go version go1.8 linux/amd64
  </code></pre>
  
  <p>go env:</p>
  
  <pre><code>azhukov@gce-machine:~$ go env
  GOARCH="amd64"
  GOBIN=""
  GOEXE=""
  GOHOSTARCH="amd64"
  GOHOSTOS="linux"
  GOOS="linux"
  GOPATH="/home/azhukov/go"
  GORACE=""
  GOROOT="/usr/local/go"
  GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
  GCCGO="gccgo"
  CC="gcc"
  GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build477416510=/tmp/go-build -gno-record-gcc-switches"
  CXX="g++"
  CGO_ENABLED="1"
  PKG_CONFIG="pkg-config"
  CGO_CFLAGS="-g -O2"
  CGO_CPPFLAGS=""
  CGO_CXXFLAGS="-g -O2"
  CGO_FFLAGS="-g -O2"
  CGO_LDFLAGS="-g -O2"
  </code></pre>
  
  <p>To me everything looks fine, I don't get why would go get return such error. It is counter-logical.</p>