Go - unbuffered channel

• Unbuffered channel causes sender and receiver synchronized, called synchronized channel
• "When a value is sent on an unbuffered channel, the receipt of the value happens before the reawakening of the sending goroutine."
  ~ Donovan, Alan A. A.. The Go Programming Language (Addison-Wesley Professional Computing Series) (p. 226). Pearson Education. Kindle Edition.
• Ex. main wait for response until goroutine send msg