I have a package that needs to run both on the native server and in a js client. I use build tags to omit code that rely on huge libraries like reflect, time and fmt. I had some very inconsistent results today where unused libraries would stick around even after I was completely sure I had excised them.

It turns out the problem was that gopherjs was reusing cached precompiled packages from $GOPATH/pkg/darwin_js and $GOPATH/pkg/darwin_js_min. When I deleted these directories and recompiled, everything worked as expected.

Easily worked around when you know it, but should probably be fixed at some point?