Merge pull request #15 from woshiqiang1/patch-1

Update sha256.md

Author: duanbiaowu

content/introduction/sha256.md

@@ -17,12 +17,12 @@ func main() {
 	h := sha256.New()
 	h.Write([]byte(s))
 	res := h.Sum(nil)
-	fmt.Printf("sha245(`hello world`) = %x\n", res)
+	fmt.Printf("sha256(`hello world`) = %x\n", res)
 }
 
 // $ go run main.go
 // 输出如下
 /**
   sha256(`hello world`) = b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9
 */
-```
+```