gps.ListPackages fails when project contains a directory named ".go"

[ascandella]

Repro case:

example-dep-ensure ❯ ls -fl
total 0
drwxr-xr-x  3 aiden  staff  102 May 10 14:18 .
drwxr-xr-x  9 aiden  staff  306 May 10 14:17 ..
drwxr-xr-x  2 aiden  staff   68 May 10 14:16 .go
example-dep-ensure ❯ dep init
gps.ListPackages: read /Users/aiden/src/go/src/github.com/sectioneight/example-dep-ensure/.go: is a directory

Proposed fix:

diff --git c/internal/gps/pkgtree/pkgtree.go i/internal/gps/pkgtree/pkgtree.go
index a83fb4e..cf6346c 100644
--- c/internal/gps/pkgtree/pkgtree.go
+++ i/internal/gps/pkgtree/pkgtree.go
@@ -203,6 +203,12 @@ func fillPackage(p *build.Package) error {
 		if filepath.Base(file)[0] == '_' {
 			continue
 		}
+
+		// Skip any directories that happen to be named ".go"
+		if stat, err := os.Stat(file); err == nil && stat.IsDir() {
+			continue
+		}
+
 		pf, err := parser.ParseFile(token.NewFileSet(), file, nil, parser.ImportsOnly|parser.ParseComments)
 		if err != nil {
 			if os.IsPermission(err) {

Wondering if there's a preferred approach. Either way I'm happy to whip up a fix and provide test cases.