import ( "fmt" "math/big" ) func main() { a := big.NewInt(123456789) b := big.NewInt(987654321) c := big.NewInt(0) c.Add(a, b) fmt.Println(c) } // Output: 1111111110
import ( "fmt" "math/big" ) func main() { a := big.NewInt(123456789) b := big.NewInt(987654321) c := big.NewInt(0) c.Mul(a, b) fmt.Println(c) } // Output: 121932631137655269
import ( "fmt" "math/big" ) func main() { a := big.NewInt(123456789) b := int64(0) b = a.Int64() fmt.Println(b) } // Output: 123456789Overall, the math.big package provides a useful set of functions for performing mathematical operations on arbitrarily large integers. This package is part of the standard Go library.