Fix some error

en/01.2.md

@@ -80,12 +80,12 @@ Write the following content to main.go.
 package main
 
 import (
-"mymath"
-"fmt"
+	"mymath"
+	"fmt"
 )
 
 func main() {
-fmt.Printf("Hello, world. Sqrt(2) = %v\n", mymath.Sqrt(2))
+	fmt.Printf("Hello, world. Sqrt(2) = %v\n", mymath.Sqrt(2))
 }
 ```
 

en/02.2.md

@@ -89,9 +89,9 @@ var isActive bool  // global variable
 var enabled, disabled = true, false  // omit type of variables
 
 func test() {
-var available bool  // local variable
-valid := false      // brief statement of variable
-available = true    // assign value to variable
+    var available bool  // local variable
+    valid := false      // brief statement of variable
+    available = true    // assign value to variable
 }
 ```	
 ### Numerical types