chore: detect Go version from go.mod when building

.forgejo/workflows/build.yaml

@@ -2,35 +2,33 @@ name: Build and test project
 
 on:
   push:
-    branches:
-      - master
+    branches: [master]
   pull-request:
-    branches:
-      - master
+    branches: [master]
 
 jobs:
 
   build:
-
     runs-on: debian-12
-    strategy:
-      matrix:
-        go-version: [ '1.22' ]
-
     steps:
-
-    - name: Checkout repo
+    -
+      name: Checkout repo
       uses: actions/checkout@v4
-
-    - name: Setup Go
+    -
+      name: Extract Go version
+      id: go-version
+      run: |
+        sed '/^go /!d; s/go /version=/' go.mod >>"$GITHUB_OUTPUT"
+    -
+      name: Setup Go
       uses: actions/setup-go@v5
       with:
-        go-version: ${{ matrix.go-version }}
-
-    - name: Build for host architecture
+        go-version: ${{ steps.go-version.outputs.version }}
+    -
+      name: Build for host architecture
       run: |
         make build
-
-    - name: Run tests
+    -
+      name: Run tests
       run: |
         make test