diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c3b6205..6e12644 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,6 +9,9 @@ on:
 jobs:
     test:
         runs-on: ubuntu-latest
+        strategy:
+            matrix:
+                go-pkg: ['go_1_17', 'go_1_18', 'go_1_19', 'go_1_20', 'go_1_21', 'go_1_22']
         steps:
             - uses: actions/checkout@v4
 
@@ -17,16 +20,29 @@ jobs:
             - name: Restore and cache Nix store
               uses: nix-community/cache-nix-action@v6.1.3
               with:
-                  primary-key: nix-${{ runner.os }}-${{ hashFiles('shell.nix') }}
+                  primary-key: nix-${{ runner.os }}-${{ matrix.go-pkg }}-${{ hashFiles('shell.nix') }}
 
             - name: Format check
-              run: nix-shell --run "test -z \$(gofmt -l .)"
+              run: nix-shell --argstr goPackage "${{ matrix.go-pkg }}" --run "test -z \$(gofmt -l .)"
 
             - name: Build
-              run: nix-shell --run "go build ./..."
+              run: nix-shell --argstr goPackage "${{ matrix.go-pkg }}" --run "go build ./..."
 
             - name: Test
-              run: nix-shell --run "go test -v -cover ./..."
+              run: nix-shell --argstr goPackage "${{ matrix.go-pkg }}" --run "go test -v -cover ./..."
 
             - name: Vet
-              run: nix-shell --run "go vet ./..."
+              run: nix-shell --argstr goPackage "${{ matrix.go-pkg }}" --run "go vet ./..."
+
+    # Rollup job for branch protection - only require this single check
+    ci:
+        runs-on: ubuntu-latest
+        needs: test
+        if: always()
+        steps:
+            - name: Check all matrix jobs passed
+              run: |
+                  if [[ "${{ needs.test.result }}" != "success" ]]; then
+                    echo "Matrix jobs failed"
+                    exit 1
+                  fi
diff --git a/README.md b/README.md
index b768e7c..0bc03ab 100644
--- a/README.md
+++ b/README.md
@@ -21,7 +21,7 @@ The implementation is in usable shape and is fairly well tested with its accompa
 Dependencies
 ------------
 
-The only requirement is [Go 1.2](http://golang.org/doc/go1.2) or later.
+The only requirement is [Go 1.17](http://golang.org/doc/go1.17) or later.
 
 Usage
 -----
diff --git a/go.mod b/go.mod
index a634d43..4ccc694 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
 module github.com/ajg/form
 
-go 1.21
+go 1.17
diff --git a/shell.nix b/shell.nix
index 152eeee..889200c 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,10 +1,32 @@
+{ goPackage ? "go" }:
+
 let
-  pkgs = import (fetchTarball
+  # Current nixpkgs (has go_1_21, go_1_22)
+  pkgsCurrent = import (fetchTarball
     "https://github.com/NixOS/nixpkgs/archive/8c5066250910.tar.gz") { };
 
-in pkgs.mkShell {
-  buildInputs = with pkgs; [
-    go
+  # nixpkgs 23.05 - has go_1_18, go_1_19, go_1_20
+  pkgs2305 = import (fetchTarball
+    "https://github.com/NixOS/nixpkgs/archive/nixos-23.05.tar.gz") { };
+
+  # nixpkgs 22.05 - has go_1_17
+  pkgs2205 = import (fetchTarball
+    "https://github.com/NixOS/nixpkgs/archive/nixos-22.05.tar.gz") { };
+
+  # Map Go packages to their source
+  goFromPkgs = {
+    go = pkgsCurrent.go;
+    go_1_17 = pkgs2205.go_1_17;
+    go_1_18 = pkgs2305.go_1_18;
+    go_1_19 = pkgs2305.go_1_19;
+    go_1_20 = pkgs2305.go_1_20;
+    go_1_21 = pkgsCurrent.go_1_21;
+    go_1_22 = pkgsCurrent.go_1_22;
+  };
+
+in pkgsCurrent.mkShell {
+  buildInputs = [
+    goFromPkgs.${goPackage}
   ];
 
   shellHook = ''