chore: pin build to Go 1.18

Minor releases of Go can change `go fmt` which can break linting.
Inconsistent formatting are just going to create annoying problems, so
the Go compiler will be pinned to the latest patch of a specific minor rev.

This should pick up security fixes without disrupting development.

We can coordinate a move to a newer Go release.

.github/workflows/pr.yml

@@ -19,7 +19,7 @@ jobs:
     - name: Set up Go 1.x
       uses: actions/setup-go@v2
       with:
-        go-version: ^1.15
+        go-version: 1.18
 
     - name: Check out code into the Go module directory
       uses: actions/checkout@v2

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:buster as builder
+FROM golang:1.18-buster as builder
 LABEL io.hockeypuck.temp=true
 RUN adduser builder --system --disabled-login
 ENV DEBIAN_FRONTEND=noninteractive

shell.nix

@@ -0,0 +1,2 @@
+with import <nixos-unstable> {};
+runCommand "dummy" { buildInputs = [ go_1_18 gnumake gcc ]; } ""