What version of Go are you using (go version)?
$ go version
go version go1.11.1 darwin/amd64
Does this issue reproduce with the latest release?
go get -u -v golang.org/x/tools/cmd/goimports
As of writing, goimports are on this commit: golang/tools@4ca4995
Regression reproducer
Please, see a reproducer repo: https://github.com/VojtechVitek/goimports-bug
Issue
Seems like latest goimports started removing completely valid import paths when package name doesn't match the pkg's directory name.