func dfs(graph map[int][]edge, visited []bool, currentVertex, parentVertex int) bool {
	visited[currentVertex] = true

	// visit all neighbours
	for _, edge := range graph[currentVertex] {
	  // If neighbour is already visited and it is NOT Parent,
    // then we have found cycle.
		if visited[edge.destination] && edge.destination != parentVertex {
			return true
		}
		if !visited[edge.destination] {
		  // Here, in modified DFS, 
		  // we will start returning value from DFS recursive function.

      // Be careful of accepting this return value 
      // and take decision based on that.
			if dfs(graph, visited, edge.destination, currentVertex) {
				return true
			}
		}
	}
	return false
}

package main

import (
	"fmt"
)

type edge struct {
	source      int
	destination int
}

func createEdge(graph map[int][]edge, source, destination int) {
	graph[source] = append(graph[source], edge{
		source:      source,
		destination: destination,
	})
}

func createGraph() map[int][]edge {
	graph := map[int][]edge{}
	createEdge(graph, 0, 1)
	createEdge(graph, 1, 0)

	createEdge(graph, 0, 2)
	createEdge(graph, 2, 0)

	createEdge(graph, 0, 3)
	createEdge(graph, 3, 0)

	createEdge(graph, 2, 3)
	createEdge(graph, 3, 2)
	return graph
}

func dfs(graph map[int][]edge, visited []bool, currentVertex, parentVertex int) bool {
	visited[currentVertex] = true

	// visit all neighbours
	for _, edge := range graph[currentVertex] {
	
	  // If neighbour is already visited and it is NOT Parent,
    // then we have found cycle.
		if visited[edge.destination] && edge.destination != parentVertex {
			return true
		}
		if !visited[edge.destination] {
			if dfs(graph, visited, edge.destination, currentVertex) {
				return true
			}
		}
	}
	return false
}

func main() {
	graph := createGraph()

	maxVertex := 3

	visited := make([]bool, maxVertex+1)
	isCyclePresent := false

	// traverse all vertices
	for i := 0; i < maxVertex; i++ {
		parentVertex := -1
		startingVertex := i
		if !visited[startingVertex] {
			isCyclePresent = dfs(graph, visited, startingVertex, parentVertex)
			if isCyclePresent {
				fmt.Printf("Cycle exist in given graph")
				break
			}
		}
	}

	if !isCyclePresent {
		fmt.Printf("Cycle does NOT exist in given graph")
	}
}

Cycle exist in given graph
Program exited.