go: upgrade to go 1.18 (#5)

Author: calebdoxsey

.github/workflows/test.yaml

@@ -11,6 +11,6 @@ jobs:
     steps:
       - uses: actions/setup-go@v2
         with:
-          go-version: 1.17.x
+          go-version: 1.18.x
       - uses: actions/checkout@v2
       - run: make test

.gitignore

@@ -0,0 +1 @@
+.vscode/

go.mod

@@ -1,6 +1,6 @@
 module github.com/pomerium/enterprise-client-go
 
-go 1.16
+go 1.18
 
 require (
 	github.com/envoyproxy/go-control-plane v0.9.9
@@ -10,3 +10,14 @@ require (
 	google.golang.org/grpc v1.40.0
 	google.golang.org/protobuf v1.27.1
 )
+
+require (
+	github.com/cncf/xds/go v0.0.0-20210312221358-fbca930ec8ed // indirect
+	github.com/davecgh/go-spew v1.1.0 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	golang.org/x/net v0.0.0-20200822124328-c89045814202 // indirect
+	golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd // indirect
+	golang.org/x/text v0.3.3 // indirect
+	google.golang.org/genproto v0.0.0-20200526211855-cb27e3aa2013 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
+)