Use Go modules (#37)

- Init Go modules
- Update GitHub Actions build workflow

Supersedes #36
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index c1fde56..1db15c1 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -4,7 +4,19 @@
   push:
     branches:
       - master
+    paths-ignore:
+      - .github/**
+      - .gitignore
+      - .whitesource
+      - codecov.yml
+      - README.md
   pull_request:
+    paths-ignore:
+      - .github/**
+      - .gitignore
+      - .whitesource
+      - codecov.yml
+      - README.md
 
 jobs:
   build:
@@ -15,13 +27,12 @@
         include:
           - go: 1.15
             build-with: true
+          - go: 1.16
+            build-with: false
     continue-on-error: ${{ matrix.build-with == false }}
     name: Build with ${{ matrix.go }}
-    defaults:
-      run:
-        working-directory: src/github.com/${{ github.repository }}
     env:
-      GOPATH: ${{ github.workspace }}
+      GO111MODULE: on
 
     steps:
     - name: Set up Go
@@ -31,9 +42,6 @@
 
     - name: Checkout code
       uses: actions/checkout@v2
-      with:
-        path: src/github.com/${{ github.repository }}
 
     - name: Vet
-      run: |
-        go vet ./...
+      run: go vet ./...
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..243ad74
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module github.com/VividCortex/godaemon
+
+go 1.12