Mutexes

Mutexes allow safe access of state across multiple goroutines. If one goroutine is r/w to a var, other goroutines are mutually excluded from accessing it.

• var m = &sync.Mutex{}
• goroutines must have access to the same mutex to lock properly
• goroutine will block if the mutex is locked, and unblock when mutex is unlocked
  • race conditions can still occur if the var is accessed without mutex protection

• mutexes can be embedded in structs:

  type currency struct {
  sync.Mutex
  amount float64
  }
  func (c *currency) Add(i float64) {
  c.Lock()
  c.amount += i
  c.Unlock()
  }

• defer c.Unlock() is useful if a function contains multiple return statements
• Read Write Mutexes allow multiple readers to hold the lock, still only one writer
  • snyc.RWMutex, with m.RLock() and m.RUnlock()