1. What version of Go are you using (go version)?
   go version go1.6 windows/amd64
2. What operating system and processor architecture are you using (go env)?

set GOARCH=amd64
set GOBIN=
set GOEXE=.exe
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOOS=windows
set GOPATH=D:\dev
set GORACE=
set GOROOT=C:\Go
set GOTOOLDIR=C:\Go\pkg\tool\windows_amd64
set GO15VENDOREXPERIMENT=1
set CC=gcc
set GOGCCFLAGS=-m64 -mthreads -fmessage-length=0
set CXX=g++
set CGO_ENABLED=1

1. What did you do?

I created two internal packages with the same name, but in different trees. I was able to reproduce the problem with the following small example.
D:\dev\src\github.com\issue\package1\internal\foo\foo.go

package foo

func Bar() {
}

and
D:\dev\src\github.com\issue\package2\internal\foo\foo.go

package foo

func Bar() {
}

Then create a file that uses the internal package.
D:\dev\src\github.com\issue\package1\main\main.go

package main

func main() {
    foo.Bar()
}

Finally, run goimports on main.go.

1. What did you expect to see?
   I expected import "github.com/issue/package1/internal/foo" to be added to main.go. Which foo to choose should have been unambiguous since the other is not importable from package1/main.
2. What did you see instead?
   goimports added import "github.com/issue/package2/internal/foo". I deleted the import statement and ran goimports several times. The package imported appeared to be random.