Error Handling (Explicit Check)

🐹 Go Language Lesson 15 Advanced

Go does not support try-catch exception handling. Instead, Go requires errors to be returned explicitly as return values, promoting clear, robust code design.

1 Explicit Return Values & The errors Package

In Go, if a function can fail, it returns an `error` object as its last return value. The caller must explicitly check if the returned error is not nil: `if err != nil { // handle error }`. While verbose, this ensures errors are handled immediately, preventing silent failures and unhandled runtime crashes.

2 Error Handling Code

Let's run a program demonstrating division verification checks and error handling patterns:

Go — Error Checks ▶ Run Code

package main

import (
    "errors"
    "fmt"
)

func validateUser(age int) (string, error) {
    if age < 0 {
        return "", errors.New("age cannot be negative")
    }
    return fmt.Sprintf("User age verified: %d", age), nil
}

func main() {
    msg, err := validateUser(-5)
    
    // Explicit error check
    if err != nil {
        fmt.Println("Error caught: ", err.Error())
    } else {
        fmt.Println(msg)
    }
}

3 Code Challenge

Challenge: Write a function called `Sqrt` that returns the square root of a float64. Return a custom error if the number is negative. Call the function in `main()` with a negative argument, check the error, and print the output.