chore: add sample application and vscode launch config

.gitignore

@@ -2,6 +2,8 @@
 /*.png
 .idea
 
+**/sample.dot
+
 # SonarQube
 .scannerwork/
 

.vscode/launch.json

@@ -0,0 +1,14 @@
+{
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "name": "Launch",
+      "type": "go",
+      "request": "launch",
+      "mode": "auto",
+      "program": "${workspaceFolder}/doc/sample.go",
+      "env": {},
+      "args": []
+    }
+  ]
+}

doc/sample.go

@@ -0,0 +1,57 @@
+package main
+
+import (
+	"log"
+	"os"
+
+	"github.com/wwmoraes/dot"
+	"github.com/wwmoraes/dot/attributes"
+)
+
+func main() {
+	log.Println("creating graph instance...")
+	rootGraph := dot.NewGraph(nil)
+
+	log.Println("creating outside node...")
+	outsideGraph := rootGraph.Node("Outside")
+
+	log.Println("creating cluster subgraph A...")
+	clusterA := rootGraph.Subgraph(&dot.GraphOptions{
+		ID:      "A",
+		Cluster: true,
+	})
+	clusterA.SetAttributeString(attributes.KeyLabel, "Cluster A")
+
+	log.Println("creating node one...")
+	insideOne := clusterA.Node("one")
+
+	log.Println("creating node two...")
+	insideTwo := clusterA.Node("two")
+
+	log.Println("creating cluster subgraph B...")
+	clusterB := rootGraph.Subgraph(&dot.GraphOptions{
+		ID:      "B",
+		Cluster: true,
+	})
+	clusterB.SetAttributeString(attributes.KeyLabel, "Cluster B")
+
+	log.Println("creating node three...")
+	insideThree := clusterB.Node("three")
+
+	log.Println("creating node four...")
+	insideFour := clusterB.Node("four")
+
+	log.Println("creating edges...")
+	outsideGraph.Edge(insideFour).Edge(insideOne).Edge(insideTwo).Edge(insideThree).Edge(outsideGraph)
+
+	log.Println("opening sample.dot file for write...")
+	fd, err := os.Create("sample.dot")
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	log.Println("writing graph to sample.dot...")
+	rootGraph.Write(fd)
+
+	log.Println("done!")
+}