Add GitHub Actions workflow for tests

.github/workflows/main.yml

@@ -0,0 +1,20 @@
+name: main
+on:
+  push:
+    branches: [main]
+    tags: [v*]
+  pull_request:
+    branches: [main]
+jobs:
+  test:
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        go: [1.18.x, 1.19.x]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/setup-go@v3
+        with:
+          go-version: ${{ matrix.go }}
+      - uses: actions/checkout@v3
+      - run: go test -v ./...

testdata/empty.yml

@@ -0,0 +1 @@
+# empty file

yaml_file_loader_test.go

@@ -45,8 +45,8 @@ func ExampleApp_Run_yamlFileLoaderDuration() {
 			Name:        "config",
 			Aliases:     []string{"c"},
 			EnvVars:     []string{"CONFIG_FILE"},
-			Value:       "../testdata/empty.yml",
-			DefaultText: "../testdata/empty.yml",
+			Value:       "testdata/empty.yml",
+			DefaultText: "testdata/empty.yml",
 			Usage:       "config file",
 		},
 		altsrc.NewDurationFlag(
@@ -78,7 +78,7 @@ func ExampleApp_Run_yamlFileLoaderDuration() {
 		},
 	}
 
-	if err := c.Run([]string{"cmd", "serve", "--config", "../testdata/empty.yml"}); err != nil {
+	if err := c.Run([]string{"cmd", "serve", "--config", "testdata/empty.yml"}); err != nil {
 		log.Fatal(err)
 	}