diff --git a/circle.yml b/circle.yml
index 08616b0..c97103d 100644
--- a/circle.yml
+++ b/circle.yml
@@ -9,9 +9,9 @@ jobs:
     - run: go get
     - run: go test -v -race
 
-  build-go-1.9:
+  build-go-1.12:
     docker:
-    - image: golang:1.9
+    - image: golang:1.12
     working_directory: /go/src/github.com/gliderlabs/ssh
     steps:
     - checkout
@@ -23,4 +23,4 @@ workflows:
   build:
     jobs:
       - build-go-latest
-      - build-go-1.9
+      - build-go-1.12
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..c43cb49
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,8 @@
+module github.com/gliderlabs/ssh
+
+go 1.12
+
+require (
+	github.com/anmitsu/go-shlex v0.0.0-20200514113438-38f4b401e2be
+	golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..294a918
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,12 @@
+github.com/anmitsu/go-shlex v0.0.0-20200514113438-38f4b401e2be h1:9AeTilPcZAjCFIImctFaOjnTIavg87rW78vTPkQqLI8=
+github.com/anmitsu/go-shlex v0.0.0-20200514113438-38f4b401e2be/go.mod h1:ySMOLuWl6zY27l47sB3qLNK6tF2fkHG55UZxx8oIVo4=
+golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e h1:gsTQYXdTw2Gq7RBsWvlQ91b+aEQ6bXFUngBGuR8sPpI=
+golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1 h1:SrN+KX8Art/Sf4HNj6Zcz06G7VEz+7w9tdXTPOZ7+l4=
+golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1 h1:v+OssWQX+hTHEmOBgwxdZxK4zHq3yOs8F9J7mk0PY8E=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=