Add support for dragonfly and netbsd
diff --git a/const_bsds.go b/const_bsds.go
index 9717374..5728243 100644
--- a/const_bsds.go
+++ b/const_bsds.go
@@ -11,7 +11,7 @@
// See the License for the specific language governing permissions and
// limitations under the License.
-// +build darwin openbsd freebsd
+// +build darwin openbsd freebsd netbsd dragonfly
package afero
diff --git a/const_win_unix.go b/const_win_unix.go
index d8f392b..968fc27 100644
--- a/const_win_unix.go
+++ b/const_win_unix.go
@@ -13,6 +13,8 @@
// +build !darwin
// +build !openbsd
// +build !freebsd
+// +build !dragonfly
+// +build !netbsd
package afero
