Go programming provides a pretty simple error handling framework with inbuilt error interface type of the following declaration −

type error interface {

   Error() string

}

Functions normally return error as last return value. Use errors.New to construct a basic error message as following −

func Sqrt(value float64)(float64, error) {

   if(value < 0){

      return 0, errors.New("Math: negative number passed to Sqrt")

   }

   return math.Sqrt(value)

}

Use return value and error message.

result, err:= Sqrt(-1)

if err != nil {

   fmt.Println(err)

}

Example

package main

import "errors"

import "fmt"

import "math"

func Sqrt(value float64)(float64, error) {

   if(value < 0){

      return 0, errors.New("Math: negative number passed to Sqrt")

   }

   return math.Sqrt(value), nil

}

func main() {

   result, err:= Sqrt(-1)

   if err != nil {

      fmt.Println(err)

   } else {

      fmt.Println(result)

   }

   result, err = Sqrt(9)

   if err != nil {

      fmt.Println(err)

   } else {

      fmt.Println(result)

   }

}

When the above code is compiled and executed, it produces the following result −

Math: negative number passed to Sqrt

3