title: Go module where package name is different to github path
body: <p>I want to add a go package to my <code>go.mod</code> file. But it's called e.g. <code>https://github.com/user/something</code> but the actual package in the source files is e.g. <code>somethingelse</code>. How can I add this to my go.mod file? Just doing this doesn't work:</p>
  <pre><code>import somethingelse github.com/user/something
  </code></pre>
  <p>I get an error:</p>
  <pre><code>module declares its path as: somethingelse
          but was required as: github.com/user/something
  </code></pre>