add CI + reduce minumum go version

.github/workflows/go-test.yaml

@@ -0,0 +1,23 @@
+name: Go Test
+
+on: [push]
+
+jobs:
+  test:
+    strategy:
+      matrix:
+        go-version: [1.15, 1.16, 1.17, 1.18, 1.19, 1.20, 1.21]  # Add or remove versions as needed
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v2
+
+    - name: Set up Go
+      uses: actions/setup-go@v2
+      with:
+        go-version: ${{ matrix.go-version }}
+
+    - name: Run tests
+      run: go test -v ./...

go.mod

@@ -1,3 +1,3 @@
 module github.com/juandspy/monkey-lang
 
-go 1.21.3
+go 1.16