improve README

README.md

@@ -1,8 +1,65 @@
 # spool
 
-
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 [![Go Reference](https://pkg.go.dev/badge/github.com/dc0d/spool.svg)](https://pkg.go.dev/github.com/dc0d/spool)
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-a simple workerpool
+
+**spool** is a simple worker-pool for Go. Each job is a `func()` which is sent to the worker-pool. A worker will pick up the job from the mailbox and execute it.
+
+First, initialize the worker-poll with a mailbox of a certain size:
+
+```go
+pool := Init(n)
+defer pool.Stop()
+```
+
+The mailbox is just a `chan func()`. In fact the worker-pool itself is defined as:
+
+```go
+type Workerpool chan func()
+```
+
+Jobs can be sent to the worker-pool in two different manners, blocking and nonblocking. To send a job to the worker-pool and block until it's completed:
+
+```go
+pool.Blocking(func() {
+    // ...
+})
+```
+
+And to send a job to the worker-pool and then move on:
+
+```go
+pool.Nonblocking(func() {
+    // ...
+})
+```
+
+As long as there is an empty space in the mailbox, `Nonblocking` will just queue the job, and moves on. When there are no more empty spaces in the mailbox, `Nonblocking` becomes blocking.
+
+A worker-pool by default has one worker. To add workers to the worker-pool:
+
+```go
+pool.Grow(9)
+```
+
+Now, the worker-pool has `10` workers, one default worker and nine added workers.
+
+It's possible to add temporary workers to the worker-pool:
+
+```go
+pool.Grow(9, WithAbsoluteTimeout(time.Minute * 5))
+```
+
+Also, instead of using and absolute timeout, an idle timeout can be used. In this case, added workers will stop, if they are idle for a certain duration:
+
+```go
+pool.Grow(9, WithIdleTimeout(time.Minute * 5))
+```
+
+The `Blocking` and `Nonblocking` methods will panic if the worker-pool is stopped - to enforce visibility on job execution.
+
+## spool serializes the jobs in single worker mode
+
+- `TODO`