A Tour of GO （2）--Flow of Control

1. For

• No parentheses and the {} are always required.
  for i:=0; i<10; i++ {
  sum +=i
  }
• The init and post statements are optional
  sum :=1
  for ; sum < 1000; {
  sum +=sum
  }
• For is Go's "while". You can drop the semicolons from above which will change to
  for sum < 1000 {
  sum +=sum
  }
  just like the "while" in c.
• Forever
  for{
  }

2. If

• No parentheses and the {} are always required.
  if x < 0 {
  }
• Short statements: to execute before the condition.
  if v := 1 ; v<10 {
  return v
  }
  • variables declared by short statement are only in the scope until the end of if（including else).
• Switch
  switch os:=runtime.GOOS; os {
  case "linux":
  fmt.pritln(xxx)
  ....
  default:
  ...
  }
  • The evaluation is from top to bottom, and stop once one of the condition is true.
  • switch with no condition is the same as switch true

3. Defer

   Defer funcs are pushed into a stack and executed in a last in first out order when the surrounding function returns.
   func main() {
   fmt.Println("counting")

      for i := 0; i < 10; i++ {
        defer fmt.Println(i)
      }
      fmt.Println("done")
   }
   

   output:
   counting
   done
   9
   8
   ...