bug: return error before creating multi pools if lbs is invalid to av…

…oid leaks (#317)

multipool.go

@@ -56,6 +56,9 @@ type MultiPool struct {
 // NewMultiPool instantiates a MultiPool with a size of the pool list and a size
 // per pool, and the load-balancing strategy.
 func NewMultiPool(size, sizePerPool int, lbs LoadBalancingStrategy, options ...Option) (*MultiPool, error) {
+	if lbs != RoundRobin && lbs != LeastTasks {
+		return nil, ErrInvalidLoadBalancingStrategy
+	}
 	pools := make([]*Pool, size)
 	for i := 0; i < size; i++ {
 		pool, err := NewPool(sizePerPool, options...)
@@ -64,9 +67,6 @@ func NewMultiPool(size, sizePerPool int, lbs LoadBalancingStrategy, options ...O
 		}
 		pools[i] = pool
 	}
-	if lbs != RoundRobin && lbs != LeastTasks {
-		return nil, ErrInvalidLoadBalancingStrategy
-	}
 	return &MultiPool{pools: pools, lbs: lbs}, nil
 }
 

multipool_func.go

@@ -45,6 +45,9 @@ type MultiPoolWithFunc struct {
 // NewMultiPoolWithFunc instantiates a MultiPoolWithFunc with a size of the pool list and a size
 // per pool, and the load-balancing strategy.
 func NewMultiPoolWithFunc(size, sizePerPool int, fn func(interface{}), lbs LoadBalancingStrategy, options ...Option) (*MultiPoolWithFunc, error) {
+	if lbs != RoundRobin && lbs != LeastTasks {
+		return nil, ErrInvalidLoadBalancingStrategy
+	}
 	pools := make([]*PoolWithFunc, size)
 	for i := 0; i < size; i++ {
 		pool, err := NewPoolWithFunc(sizePerPool, fn, options...)
@@ -53,9 +56,6 @@ func NewMultiPoolWithFunc(size, sizePerPool int, fn func(interface{}), lbs LoadB
 		}
 		pools[i] = pool
 	}
-	if lbs != RoundRobin && lbs != LeastTasks {
-		return nil, ErrInvalidLoadBalancingStrategy
-	}
 	return &MultiPoolWithFunc{pools: pools, lbs: lbs}, nil
 }