[TOC] ## go 沒有重入鎖的解決辦法 bad ``` func Withdraw(amount int) bool { mu.Lock() defer mu.Unlock() Deposit(-amount) if Balance() < 0 { Deposit(amount) // 在已經上鎖的情況下在調用Deposit會出現死鎖 return false } return true } func Deposit(amount int) { mu.Lock() defer mu.Unlock() balance += amount } ``` good ``` //降低函數的顆粒度 func Withdraw(amount int) bool { mu.Lock() defer mu.Unlock() deposit(-amount) if balance < 0 { deposit(amount) return false // insufficient funds } return true } func Deposit(amount int) { mu.Lock() defer mu.Unlock() deposit(amount) } func Balance() int { mu.Lock() defer mu.Unlock() return balance } //拆成更小的函數 func deposit(amount int) { balance += amount } ```