add an example

README.md

@@ -277,6 +277,53 @@ func main() {
 </tr>
 </table>
 
+Concurrently map a slice:
+
+<table>
+<tr>
+<th><code>stdlib</code></th>
+<th><code>conc</code></th>
+</tr>
+<tr>
+<td>
+
+```go
+func concMap(input []int, f func(int) int) []int {
+	res := make([]int, len(input))
+	var idx atomic.Int64
+
+	var wg sync.WaitGroup
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+
+			for {
+				i := int(idx.Add(1) - 1)
+				if i >= len(input) {
+					return
+				}
+
+				res[i] = f(input[i])
+			}
+		}()
+	}
+	wg.Wait()
+	return res
+}
+```
+</td>
+<td>
+
+```go
+func concMap(input []int, f func(int) int) []int {
+	iter.Map(input, f)
+}
+```
+</td>
+</tr>
+</table>
+
 Process an ordered stream concurrently: