Cap returns the capacity of this default pool.

Free returns the available goroutines to work.

初始化协程池：默认池子大小 很大很大.

NewPool generates an instance of ants pool.

NewPoolWithFunc generates an instance of ants pool with a specific function.

Release Closes the default pool.

Running returns the number of the currently running goroutines.

Submit submits a task to pool.

CLOSED represents that the pool is closed.

DEFAULT_ANTS_POOL_SIZE is the default capacity for a default goroutine pool.

DEFAULT_CLEAN_INTERVAL_TIME is the interval time to clean up goroutines.

ErrInvalidPoolExpiry will be returned when setting a negative number as the periodic duration to purge goroutines.

ErrInvalidPoolSize will be returned when setting a negative number as pool capacity.

ErrLackPoolFunc will be returned when invokers don't provide function for pool.

ErrPoolClosed will be returned when submitting task to a closed pool.

ErrPoolOverload will be returned when the pool is full and no workers available.

Pool accept the tasks from client, it limits the total of goroutines to a given number by recycling goroutines.

PoolWithFunc accept the tasks from client, it limits the total of goroutines to a given number by recycling goroutines.