title: how to install a package with gvm(Go Version Manager)? go get failed
body: <p>I successfully installed <code>go1.6.2</code> with <code>gvm</code> and used <code>global</code> pkgset.<br />
  I am trying to install <code>gocode</code> package with gvm, but <code>go get</code> not working.<br />
  I guess gvm is not really stable yet?</p>
  <pre><code>➜  ~ gvm use 1.6.2
  Now using version go1.6.2
  ➜  ~ gvm pkgset use global
  Now using version go1.6.2@global
  ➜  ~  go get -u github.com/nsf/gocode
  ➜  ~ go list
  can't load package: package .: no buildable Go source files in /Users/seoyoochan
  
  ➜  ~ go install gocode
  can't load package: package gocode: cannot find package &quot;gocode&quot; in any of:
      /Users/seoyoochan/.gvm/gos/go1.6.2/src/gocode (from $GOROOT)
      /Users/seoyoochan/.gvm/pkgsets/go1.6.2/global/src/gocode (from $GOPATH)
      /Users/seoyoochan/.gvm/pkgsets/go1.6.2/global/src/gocode
  </code></pre>