diff --git a/.circleci/config.yml b/.circleci/config.yml
index 8433d36..8e0b18d 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -9,9 +9,11 @@ workflows:
       - go-test:
           name: Go 1.14
           docker-image: circleci/golang:1.14
+          build-as-module: true
       - go-test:
           name: Go 1.13
           docker-image: circleci/golang:1.13
+          build-as-module: true
       - go-test:
           name: Go 1.12
           docker-image: circleci/golang:1.12
@@ -35,6 +37,9 @@ jobs:
     parameters:
       docker-image:
         type: string
+      build-as-module:
+        type: boolean
+        default: false
 
     docker:
       - image: <<parameters.docker-image>>
@@ -49,7 +54,11 @@ jobs:
     steps:
       - checkout
       - run: go get -u $COMMON_GO_PACKAGES
-      - run: go get -t .
+
+      - unless:
+          condition: <<parameters.build-as-module>>
+          steps:
+            - run: go get -t .
       
       - run:
           name: Run tests
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..d630210
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module github.com/launchdarkly/go-ntlmssp
+
+go 1.13
+
+require golang.org/x/crypto v0.0.0-20200604202706-70a84ac30bf9
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..ce78ae2
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,7 @@
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20200604202706-70a84ac30bf9 h1:vEg9joUBmeBcK9iSJftGNf3coIG4HqZElCPehJsfAYM=
+golang.org/x/crypto v0.0.0-20200604202706-70a84ac30bf9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=