-- want --
valid:
valid.go

omitted:
vendor/x/y: file is in vendor directory
sub/go.mod: file is in another module
.hg_archival.txt: file is inserted by 'hg archive' and is always omitted

invalid:
not/../clean: file path is not clean
GO.MOD: go.mod files must have lowercase names
invalid.go': malformed file path "invalid.go'": invalid char '\''
valid.go: multiple entries for file "valid.go"
-- valid.go --
-- not/../clean --
-- GO.MOD --
-- invalid.go' --
-- vendor/x/y --
-- sub/go.mod --
-- .hg_archival.txt --
-- valid.go --
duplicate
-- valid.go --
another duplicate