build: add build workflow

.github/workflows/build.yml

@@ -0,0 +1,26 @@
+name: Build Go
+
+on:
+  push:
+    branches: [ "main" ]
+
+jobs:
+
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Set up Go
+      uses: actions/setup-go@v4
+      with:
+        go-version: '1.23'
+
+    - name: Build
+      run: go build
+
+    - name: Upload build
+      uses: actions/upload-artifact@v4
+      with:
+        name: holesail-proxy
+        path: holesail-proxy