Upgrade to go 1.18 to get generics

Originally wanted to upgrade to 1.25, but test woulds pass anymore.
Upgrading to 1.18 allows us to use generics while preventing any
additional maintenance as all tests still passes.

Author: Florimond

.github/workflows/tests.yaml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: [ '1.15', 'stable' ]
+        go: [ '1.18', 'stable' ]
     name: Tests on Go ${{ matrix.go }}
     steps:
       - name: Checkout Repo

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.16-alpine3.13 AS build-go
+FROM golang:1.18-alpine AS build-go
 
 ARG GIT_SSH_KEY
 ARG KNOWN_HOSTS_CONTENT

go.mod

@@ -1,8 +1,16 @@
 module github.com/Workiva/go-datastructures
 
-go 1.15
+go 1.18
 
 require (
 	github.com/stretchr/testify v1.7.0
 	github.com/tinylib/msgp v1.1.5
 )
+
+require (
+	github.com/davecgh/go-spew v1.1.0 // indirect
+	github.com/philhofer/fwd v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/stretchr/objx v0.1.0 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
+)