Add big int for fo

categories/go.md

@@ -59,6 +59,40 @@ msg := <-messages
 ```go
 ch := make(chan Task, 3)
 ```
+## Big Numbers
+
+Package big implements arbitrary-precision arithmetic (big numbers).
+For example the int numbers larger than `int64` or the float greater than `float64`.
+
+```
+int16: (-32,768 to +32,767)
+
+int32: (-2,147,483,648 to +2,147,483,647)
+
+int64: (-9,223,372,036,854,775,808 to +9,223,372,036,854,775,807)
+```
+The following numeric types are supported:
+```
+ Int    signed integers
+ Rat    rational numbers
+ Float  floating-point numbers
+```
+
+Some exmaple code
+```go
+import "math/big"
+
+//string to Int
+n1 := new(big.Int)
+n1, ok = n1.SetString(str1, 10)
+
+// Int1 + Int2
+result := new(big.Int)
+result.Add(n1, n2)
+
+// Int to string
+result.String()
+```
 
 ## Sync
 
@@ -150,14 +184,14 @@ return p.count
 // more readable
 ```
 
-# Frameworks
+## Frameworks
 
-## db
+### db
 
 - xorm
 - gorm
 
-## web
+### web
 
 - beego
 - mux