title: no obvious way to disable test caching in go 1.10
body: <p>Golang 1.10 introduced caching for test, but there is no obvious way to disable test caching.
  So the question is, how to temporal dislable it and how to force rebuild it.
  I did read the documentation: <a href="https://golang.org/cmd/go/#hdr-Build_and_test_caching" rel="noreferrer">https://golang.org/cmd/go/#hdr-Build_and_test_caching</a> but did not found any obvious answer to that question.</p>