From 684b0a09b87b8c8dee7554e04842355bd0450d39 Mon Sep 17 00:00:00 2001
From: oscarzhou <oscarzhou0727@icloud.com>
Date: Mon, 26 Apr 2021 20:40:06 +1200
Subject: [PATCH] doc: add explanation of the keywords used with goroutine

---
 README.md | 37 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 7354166..2f78b11 100644
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 # go-concurrency
 
-Aims to learn the knowledge about concurrency in Go
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+Aims to learn the knowledge about concurrency in Go
+
+## Flow control with channels
+
+
+1. We can imagine that channel is a pipe, `chan<-` means to send a value into the channel. `<-chan` means to receive a value from the channel.  
+
+2. `select ... case` can execute sending value into a channel
+
+
+## Range and Close
+
+1. A sender can close a channel to indicate that no more values will be sent.  
+2. Receivers can test whether a channel has been closed by assigning a second parameter to the receive expression. `v, ok := <-ch`, `ok` is `false` if there are no more values to receive and the channel is closed.  
+3. The loop for `i:= range c` receives values from the channel repeatedly until it is closed.  
+4. Only the sender should close a channel, never the receiver. Sending on a closed channel will cause a panic.  
+5. Channels aren't like files; you don't usually need to close them. Closing is only necessary when the receiver must be told there are no more values coming, such as to terminate a `range` loop.  
+
+
+## Select 
+
+1. The `select` statement lets a goroutine wait on multiple communication operations  
+2. A `select` blocks until one of its cases can run, then it executes that case. It chooses one at random if multiple are ready  
+
+## Default selection
+
+1. The `default` case in a `select` is run if no other case is ready.  
+2. Use a `default` case to try a send or receive without blocking  
+```
+select {
+    case i:= <-c:
+        // use i
+    default: 
+        // receive when c is blocked        
+}
+```
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