Move all backends into backend directory

backend/sftp/stringlock_test.go

@@ -0,0 +1,40 @@
+package sftp
+
+import (
+	"fmt"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestStringLock(t *testing.T) {
+	var wg sync.WaitGroup
+	counter := [3]int{}
+	lock := newStringLock()
+	const (
+		outer = 10
+		inner = 100
+		total = outer * inner
+	)
+	for k := 0; k < outer; k++ {
+		for j := range counter {
+			wg.Add(1)
+			go func(j int) {
+				defer wg.Done()
+				ID := fmt.Sprintf("%d", j)
+				for i := 0; i < inner; i++ {
+					lock.Lock(ID)
+					n := counter[j]
+					time.Sleep(1 * time.Millisecond)
+					counter[j] = n + 1
+					lock.Unlock(ID)
+				}
+
+			}(j)
+		}
+	}
+	wg.Wait()
+	assert.Equal(t, [3]int{total, total, total}, counter)
+}