title: Go 1.11 ignores the `vendor` directory, the errors give the impression the directory is never even looked at
body: <p>I'm having the issue of Go 1.11.4 ignoring the <code>vendor</code> directory of the project I'm in.</p>
  
  <p>When trying to run various commands, I get the following errors, even though the paths referenced are clearly present in the vendor directory.  The error message itself appears to indicate that the <code>vendor</code> directory is not even being looked at, at least not for this project that supposedly couldn't be found.</p>
  
  <p>What exactly is going on, and how do I even troubleshoot this?</p>
  
  <p>Below is a straight copy/paste from the terminal, after some <code>pbpaste | sed "s#…#R#g;s#…#M#g;s#…#D#g;s#…#B#g;s#…#example.org#g;s#^#</code>printf \t<code>#g" | pbcopy</code> script to anonymise the repositories.</p>
  
  <pre><code>ubuntu:R {607} go version
  go version go1.11.4 linux/amd64
  ubuntu:R {608} go build | &amp; head -4
  server.go:10:2: cannot find package "example.org/M/B" in any of:
      /usr/local/go/src/example.org/M/B (from $GOROOT)
      /home/ubuntu/go/src/example.org/M/B (from $GOPATH)
  R.go:8:2: cannot find package "example.org/M/D" in any of:
  ubuntu:R {609} ll vendor/example.org/M/B/
  total 28
  4 -rw-r--r-- 1 ubuntu ubuntu  156 Jan 10 17:57 .drone.yml
  8 -rw-r--r-- 1 ubuntu ubuntu 6207 Jan 10 17:57 Gopkg.lock
  4 -rw-r--r-- 1 ubuntu ubuntu  798 Jan 10 17:57 Gopkg.toml
  4 -rw-r--r-- 1 ubuntu ubuntu   53 Jan 10 17:57 README.md
  8 -rw-r--r-- 1 ubuntu ubuntu 4783 Jan 10 17:57 B.go
  ubuntu:R {610} go env
  GOARCH="amd64"
  GOBIN=""
  GOCACHE="/home/ubuntu/.cache/go-build"
  GOEXE=""
  GOFLAGS=""
  GOHOSTARCH="amd64"
  GOHOSTOS="linux"
  GOOS="linux"
  GOPATH="/home/ubuntu/go"
  GOPROXY=""
  GORACE=""
  GOROOT="/usr/local/go"
  GOTMPDIR=""
  GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
  GCCGO="gccgo"
  CC="gcc"
  CXX="g++"
  CGO_ENABLED="1"
  GOMOD=""
  CGO_CFLAGS="-g -O2"
  CGO_CPPFLAGS=""
  CGO_CXXFLAGS="-g -O2"
  CGO_FFLAGS="-g -O2"
  CGO_LDFLAGS="-g -O2"
  PKG_CONFIG="pkg-config"
  GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build981837178=/tmp/go-build -gno-record-gcc-switches"
  ubuntu:R {611} 
  </code></pre>