concurrency problem with golang

thing.go

	files, err := ioutil.ReadDir("./plugins/")
	if err != nil {
		panic(err)
	}

	var plugin_group sync.WaitGroup
	plugin_group.Add(len(files))
	for _, f := range files {
		fmt.Println("Found: " + f.Name())

		go func() {
			defer plugin_group.Done()

			content, err := ioutil.ReadFile("./plugins/" + f.Name())
			if err != nil {
				panic(err)
			}

			fmt.Println(string(content))
		}()
	}

	plugin_group.Wait()
	
	/*
$ cat plugins/test.rb
puts "testing mruby"

$ cat plugins/test2.rb
"do a thing"

$ cat plugins/test3.rb
1 + 4

Output:
Found: test.rb
Found: test2.rb
Found: test3.rb
1 + 4

1 + 4

1 + 4

*/