代码格式fix

ch9/ch9-07.md

@@ -163,12 +163,13 @@ type Memo struct {
 
 // Get is concurrency-safe.
 func (memo *Memo) Get(key string) (value interface{}, err error) {
-	res, ok := memo.cache[key] if!ok{
+    res, ok := memo.cache[key]
+    if !ok {
 	res.value, res.err = memo.f(key)
 	memo.cache[key] = res
 	memo.mu.Lock()
 	res, ok := memo.cache[key]
-	if !ok {
+    if !ok {
 		res.value, res.err = memo.f(key)
 		memo.cache[key] = res
 	}